Moist Rhubarb Sourdough Discard Cake (with Lemon & Honey!)

Introduction & Inspiration

As a sourdough baker, I’m always on the hunt for creative and delicious ways to use up my sourdough discard, and this recipe for a Moist Rhubarb Sourdough Discard Cake immediately captured my imagination! It promises a wonderfully tender, moist snack cake infused with a subtle tang from the discard, packed with tart rhubarb chunks, brightened with lemon zest, and sweetened with honey and cane sugar. The beautiful rhubarb pattern on top makes it a true showstopper.

My inspiration for diving into this particular recipe came from wanting a simple, single-layer cake that celebrates the flavors of spring and summer. Rhubarb is a favorite of mine, and the idea of pairing its tartness with the complex background notes of sourdough discard in a moist, oil-based cake sounded absolutely divine.

My goal is to guide you step-by-step through making this unique and flavorful cake. We’ll cover how to incorporate sourdough discard seamlessly, the clever trick to prevent rhubarb from sinking, and the specific two-temperature baking method that ensures a perfectly cooked cake. It’s a fantastic way to give your sourdough discard a delicious new purpose.

Let’s get ready to bake a truly special rhubarb cake!

Nostalgic Appeal / Comfort Food Connection

This Rhubarb Sourdough Discard Cake, while featuring the modern and popular element of sourdough discard, is deeply rooted in the comforting nostalgia of homemade snack cakes and seasonal fruit baking. Simple, single-layer cakes studded with fruit are a classic comfort food, evoking memories of after-school treats, bake sales, and cozy afternoons with a cup of tea.

Rhubarb itself is a nostalgic ingredient for many, often associated with springtime gardens, grandma’s recipes, and that unique, beloved sweet-tart flavor found in pies, crumbles, and jams. Combining this classic seasonal fruit with a tender, moist cake feels both wonderfully familiar and satisfying.

The use of sourdough discard taps into a long tradition of resourceful baking, using every part of the starter to create something delicious. It’s a practice that feels both modern in its popularity and comfortingly old-fashioned in its no-waste ethos.

Making and enjoying this cake feels like savoring a piece of home-baked comfort, thoughtfully crafted with a unique blend of traditional and contemporary elements.

Homemade Focus (Sourdough Discard & Fresh Rhubarb)

This Rhubarb Sourdough Discard Cake recipe is a wonderful celebration of creating a unique and flavorful cake from scratch, highlighting the creative use of sourdough discard and fresh, seasonal rhubarb. The focus is on building a tender, moist crumb and a balanced flavor profile through simple yet effective homemade techniques.

I love recipes that showcase clever tricks, and the method here of tossing the chopped rhubarb in a bit of the dry flour mixture before folding it into the batter is a classic homemade technique. This simple step helps prevent the heavy fruit pieces from sinking to the bottom, ensuring they are beautifully distributed throughout the cake.

Crafting the batter with sourdough discard, oil, honey, and fresh lemon zest is another key homemade aspect that results in a complex flavor and exceptionally moist texture. The final touch of arranging longer pieces of rhubarb on top in a decorative pattern before baking adds a beautiful, artisanal finish.

From incorporating your own sourdough discard to carefully arranging the rhubarb topping, every step of this recipe emphasizes the rewarding process of creating a special, flavorful, and visually appealing homemade cake.

Flavor Goal

The primary flavor goal of this Moist Rhubarb Sourdough Discard Cake is a delightful and harmonious balance of tart rhubarb, a subtly tangy and incredibly tender cake crumb, and a gentle sweetness from cane sugar and honey, all brightened by fresh lemon zest and warm vanilla.

The cake itself, made with oil, milk, and sourdough discard, should be exceptionally moist and tender. The sourdough discard should provide a subtle, complex tang that enhances the other flavors without being overly sour. Honey and lemon zest add aromatic sweetness and bright citrus notes.

The rhubarb, both the chunks baked within the cake and the decorative pieces on top, becomes soft and tender, providing pockets of tart, fruity flavor that cut through the richness of the cake.

Sprinkling the top with cane sugar before baking creates a delicate, slightly crisp crust. The overall effect is a sophisticated yet comforting snack cake that is moist, tender, tangy, tart, sweet, and beautifully balanced.

Ingredient Insights

Let’s explore the key components that make this cake so unique and delicious:

• Fresh rhubarb: The star fruit! Provides tartness and moisture. The recipe cleverly uses it in two ways: chopped chunks inside and longer pieces for a decorative top. Removing any tough outer strings is a good practice.
• All-purpose flour: Provides the main structure for the cake.
• Baking powder & Baking soda: Leavening agents. The user’s prompt listed only baking powder in the instructions but the ingredient list in a previous similar prompt for zucchini bread included both. Given the presence of acidic sourdough discard, honey, and lemon juice, using both baking powder and baking soda for lift and browning would be logical. I will assume the prompt for a different recipe was a copy-paste error and that this Rhubarb cake recipe intended baking powder only, as listed in its own ingredients. Correction: The user’s provided ingredients for this specific recipe list only baking powder, so I will stick to that. It will still provide ample lift.
• Cane sugar: Sweetens the cake. A small amount is reserved for the topping.
• Sunflower or grapeseed oil: A neutral oil that contributes to a very moist crumb that stays tender even when chilled.
• Lemon zest & Fresh lemon juice: Provide essential brightness and fresh citrus flavor that pairs beautifully with rhubarb.
• Eggs: Add structure, richness, and binding. Room temperature is best.
• Runny honey: Adds a nuanced, floral sweetness and contributes to moisture.
• Sourdough discard: The unique ingredient! Adds a subtle tangy flavor complexity and can contribute to a tender texture. Using it at room temperature is recommended for easier incorporation.
• Vanilla extract: Enhances the sweet and warm flavors.
• Whole milk: Adds moisture and richness.

The combination of sourdough discard, oil, honey, and lemon creates a wonderfully complex and moist cake base.

Essential Equipment

You’ll need standard cake-baking tools:

• An 8-inch square cake pan (as specified, though a 9-inch is noted as an alternative): A metal pan is generally preferred for even baking.
• Grease and Flour, or Parchment paper: For preparing the pan to prevent sticking. Lining with parchment is highly recommended for easy removal.
• A Stand mixer or a Handheld electric mixer: Recommended for creaming the oil and sugar and incorporating the eggs properly.
• Mixing bowls (medium for dry ingredients, large for batter).
• A Whisk: For combining dry ingredients.
• A Rubber spatula: For folding in the rhubarb and scraping the bowl.
• A Cutting board and knife: For preparing the rhubarb.
• A Zester/Microplane and Juicer: For the lemon.
• Measuring cups and spoons (and a kitchen scale for gram measurements, if you prefer accuracy).
• Wire rack: For cooling the baked cake.

An electric mixer helps create a smooth, frothy base for the batter.

List of Ingredients with Measurements

Here’s the complete list of ingredients, with precise measurements (using provided weights where available for clarity):

• 8 ounces fresh rhubarb, divided (¾ for inside, ¼ for topping)
• 170 grams (approx. 1 ⅓ cups) all-purpose flour
• 1 1/2 teaspoons baking powder
• 1/2 teaspoon fine sea salt
• 155 grams (approx. ¾ cup) cane sugar, divided (145g for batter, 10g for topping)
• 1/2 cup sunflower or grapeseed oil
• 2 teaspoons lemon zest (from about 1 large lemon)
• 2 large eggs, room temperature
• 2 1/2 tablespoons runny honey
• 65 grams (approx. ¼ cup) sourdough discard, preferably room temperature
• 1 1/2 teaspoons vanilla extract
• 1 tablespoon fresh lemon juice
• 2 1/2 tablespoons whole milk
• (Implied: Grease and flour for pan)

These quantities are perfect for an 8-inch square cake pan.

Have rhubarb prepped and sourdough discard at room temperature before starting.

Step-by-Step Instructions (Crafting Your Sourdough Discard Cake!)

Let’s bake this unique and moist Rhubarb Sourdough Discard Cake:

1. Preheat Oven and Prepare Pan & Rhubarb:

• Preheat your oven to 350°F (175°C).
• Grease and line an 8-inch square cake pan with parchment paper, leaving an overhang on two sides to act as “handles” for easy removal.
• Prepare your rhubarb: Wash and trim the rhubarb stalks. Cut about ¾ of the rhubarb (6 oz) into ½-inch chunks. Cut the remaining ¼ of the rhubarb (2 oz) into longer, thinner pieces that will fit nicely on top of the cake in a decorative pattern. Place the ½-inch chunks into a medium bowl.

2. Prepare Dry Ingredients & Coat Rhubarb:

• In another medium bowl, whisk together the all-purpose flour, baking powder, and fine sea salt until well combined.
• Scoop 2 heaping teaspoons from this flour mixture and add it to the bowl with the chopped ½-inch rhubarb chunks. Toss the rhubarb gently until it is lightly coated in flour. This clever trick helps prevent the rhubarb from sinking to the bottom of the cake. Set both bowls aside.

3. Mix the Wet Ingredients:

• In the bowl of a stand mixer fitted with the paddle attachment (or in a large bowl using a handheld electric mixer), add 145 grams (most of your measured amount) of the cane sugar, the sunflower or grapeseed oil, and the lemon zest.
• Beat on medium speed for 1 minute. This step helps dissolve the sugar and releases the fragrant oils from the lemon zest.
• Add the room temperature eggs and beat for another 30 seconds on medium speed, until the mixture is pale, frothy, and well combined. Scrape down the sides of the bowl.
• Add the honey, room temperature sourdough discard, vanilla extract, fresh lemon juice, and whole milk to the bowl. Mix on medium speed until these ingredients are just combined.

4. Combine Wet and Dry to Make Batter:

• With the mixer on low speed, gradually add the dry ingredient mixture (from Step 2) to the wet ingredient mixture.
• Mix just until no dry bits of flour remain. Do not overmix! Overmixing will develop gluten and can make the cake tough.

5. Fold in Rhubarb and Assemble:

• Gently fold the flour-coated rhubarb chunks into the prepared batter using a rubber spatula.
• Pour the batter into the prepared 8-inch cake pan and use the spatula to smooth the top into an even layer.
• Arrange the longer, decorative pieces of rhubarb on top of the batter in any pattern you’d like.
• Sprinkle the top of the cake evenly with the remaining 10 grams (about 2 heaping teaspoons) of cane sugar.

6. Bake the Cake (Two-Temperature Method):

• Place the cake pan in the preheated 350°F (175°C) oven.
• Bake for 25 minutes.
• After 25 minutes, turn the oven down to 330°F (165°C).
• Continue to bake for about 15 minutes more. The cake is done when a toothpick inserted into the center comes out with a few moist (but not wet) crumbs attached. For a 9-inch cake pan, adjust times as noted in the original recipe (20 mins at 350°F, then 8-10 mins at 330°F). Be careful not to overbake.

7. Cool and Serve:

• Remove the cake from the oven and let it cool completely on a wire rack in the pan.
• Once completely cool, use the parchment paper overhang to lift the cake out of the pan.
• Slice and serve. In a sealed container, this cake stores very well in the refrigerator for up to 4 days.

The two-temperature bake helps the cake set and cook through evenly without over-browning.

Troubleshooting

Quick breads and cakes with fresh fruit and sourdough can have nuances:

• Problem: Cake is dense or tough.
  • Solution: Overmixing the batter after adding the flour is the most likely cause. Mix only until the flour streaks disappear. Ensure baking powder is fresh.
• Problem: Cake is underbaked or gooey in the center.
  • Solution: It needed more baking time. Oven temperatures vary, and the moistness of the rhubarb and sourdough can affect bake times. Always rely on the toothpick test for doneness. If the top is browning too quickly, loosely tent the pan with foil for the remaining bake time.
• Problem: Rhubarb chunks all sank to the bottom.
  • Solution: Tossing the rhubarb chunks in a bit of the flour mixture, as directed, is the best way to prevent this. A thick batter, which this recipe should have, also helps suspend the fruit.
• Problem: Sourdough discard flavor is too strong.
  • Solution: The flavor of sourdough discard varies greatly depending on its age and hydration. For a milder flavor, use discard that is relatively “young” (fed more recently) rather than discard that has been sitting in the fridge for a long time and has developed a very acidic or “hoochy” character.

Don’t overmix, and trust the toothpick test for doneness!

Tips and Variations

Let’s customize this unique and delicious cake:

• Tip: Use fresh, crisp rhubarb stalks. If your rhubarb is particularly wide or has tough outer strings, you can peel those off before chopping.
• Variation: Add other warm spices to the dry ingredients, such as ½ teaspoon of ground ginger (as used in a previous pie recipe) or ¼ teaspoon of ground cardamom, both of which pair beautifully with rhubarb and lemon.
• Tip: For the best lemon flavor, don’t skip rubbing the zest into the sugar! It makes a noticeable difference in the aroma and taste of the finished cake.
• Variation: Substitute other fruits for the rhubarb. Diced tart apples (like Granny Smith) or a mix of berries would be delicious. Adjust baking time as needed.
• Tip: If you don’t have sourdough discard, you can still make a lovely rhubarb cake, but the unique tang will be missing. You might need to adjust liquids slightly; some recipes would substitute the discard with more yogurt or milk.
• Variation: Instead of just a sugar sprinkle, top the cooled cake with a simple lemon glaze (powdered sugar + lemon juice) or a dollop of crème fraîche or sweetened whipped cream when serving.
• Variation: Fold ½ cup of chopped walnuts, pecans, or pistachios into the batter for added nutty crunch.

A wonderful base for a variety of seasonal snack cakes!

Serving and Pairing Suggestions

This Moist Rhubarb Sourdough Discard Cake is a delightful snack cake or simple dessert.

Serving: Serve at room temperature or slightly chilled, cut into squares or slices.

Pairing:

• As is: Delicious on its own as a snack or for breakfast.
• With a Topping: A dollop of Greek yogurt, crème fraîche, or lightly sweetened whipped cream complements the tart rhubarb perfectly.
• Beverages: Excellent with a cup of hot coffee, black tea, or an herbal tea like chamomile or ginger.

Its moist texture and balanced sweet-tart flavor make it appealing any time of day.

Nutritional Information

This cake features fruit, whole wheat (in previous similar recipes, but not this one), and sourdough discard. Nutritional info is approximate (per serving, assuming 9-12 squares from an 8×8 pan):

• Calories: 250-350
• Fat: 12-20 grams (mostly from oil)
• Saturated Fat: 1-3 grams (if using vegetable oil)
• Cholesterol: 30-50+ mg (from eggs)
• Sodium: 150-250+ mg
• Total Carbs.: 30-40+ grams
• Dietary Fiber: 1-3 grams (from rhubarb and flour)
• Sugars: 18-28+ grams (from sugar and honey)
• Protein: 3-5 grams

Provides some fiber from the rhubarb. The use of oil keeps saturated fat lower than a butter-based cake. Sugar content is notable, as with most cakes.

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Recipe Summary and Q&A

Let’s conclude with a summary and common questions:

Recipe Summary:

Moist Rhubarb Sourdough Discard Cake is a single-layer snack cake made with a batter enriched with whole milk Greek yogurt, olive oil, and sourdough discard for a tender, moist crumb and a subtle tang. The cake is studded with chopped fresh rhubarb (tossed in flour to prevent sinking) and topped with decorative rhubarb pieces and a sprinkle of sugar. It’s baked using a two-temperature method to ensure it cooks through perfectly.

Q&A:

Q: Can I make this cake ahead of time? A: Yes, this cake stores very well. Bake and cool completely. The recipe notes it can be stored in a sealed container in the refrigerator for up to 4 days.

Q&A: How do I store this cake? A: Store in a sealed, airtight container. It can be kept at room temperature for 1-2 days or in the refrigerator for up to 4 days as recommended. The moisture from the zucchini (oops, rhubarb!) keeps it from drying out quickly.

Q&A: Can I freeze this cake? A: Yes, it should freeze well. Cool completely, then wrap the whole cake or individual slices tightly in plastic wrap and then foil. Freeze for up to 3 months. Thaw at room temperature or in the refrigerator.

Q&A: What does the sourdough discard do in this recipe? A: Sourdough discard (unfed starter) adds a subtle, complex, tangy flavor to the cake that beautifully complements the tartness of the rhubarb and the sweetness of the sugar/honey. It also contributes to a very tender and moist crumb. It is not used for leavening here; the baking powder does that work.

Q&A: Can I use frozen rhubarb? A: Yes. Thaw the frozen rhubarb completely and drain it very thoroughly, patting it dry with paper towels to remove as much excess moisture as possible before chopping and tossing with flour. Excess water can make the cake soggy.