Let’s break down the process:

Make the Lemon Cake:

1. Prepare Oven and Pan: Butter a 9-inch cake pan. Preheat oven to 300ºF (150ºC).
2. Combine Dry Ingredients: In a small bowl, whisk together the flour, baking powder, baking soda, and salt.
3. Cream Butter and Sugar: In a large bowl, cream together the softened butter and sugar until light and fluffy.
4. Add Egg and Extracts: Add the egg and beat well. Beat in the vanilla and lemon extracts.
5. Alternate Dry and Wet Ingredients: Add half of the dry ingredients to the wet ingredients and mix. Add the buttermilk and beat. Add the remaining dry ingredients and mix just until combined. Do not overmix.
6. Bake: Pour the batter into the prepared pan, smooth it out, and bake in the preheated oven until lightly browned and a toothpick inserted in the center comes out clean, about 30 minutes.
7. Cool: Cool completely before making the trifles.

Make the Sweetened Whipped Cream:

1. Whip Ingredients: In a medium bowl, whip the heavy cream, vanilla (either paste or extract), and maple syrup (or sugar) until medium-stiff peaks form.

Assemble the Trifles:

1. Prepare Cake: Slice half of the cooled lemon cake into small cubes.
2. Layer Ingredients: Place a few of the cake cubes in the bottom of a half-pint (8-ounce) jam jar. Add a dollop or two of the whipped cream. Drop in a layer of blueberries. Spread a spoonful of lemon curd on top. Repeat the layers once more.
3. Repeat: Do the same with the remaining jam jars.
4. Serve of Chill Serve immediately or store, covered, in the refrigerator for a few hours.

These are detailed and easy to understand instructions.