Turn your leftover sourdough starter into the most delicious lemon sheet cake with fluffy texture and bright lemon flavor.
Prep Time:15 minutesmins
Cook Time:35 minutesmins
Total Time:50 minutesmins
Equipment
stand mixer or hand mixer
Large mixing bowl
saucepan
13x9 inch baking pan
Ingredients
Cake
2cupsall-purpose flour
1teaspoonsalt
1½teaspoonsbaking powder
½teaspoonbaking soda
4large eggs
1¾cupssugar
¾cupsourdough discard100% hydration, at room temp
¾cupmilk
¼cupbutterroom temperature (cut into tablespoon pieces)
⅓cupvegetable oil
2tablespoonslemon zest
1½tablespoonslemon juice
2-3drops yellow food coloringoptional
Lemon Buttercream
1cupunsalted buttersoftened (2 sticks)
4cupspowdered sugar
1½tablespoonslemon zest
2tablespoonsfresh lemon juice
2tablespoonsheavy cream
Pinchsalt
Additional lemon slices or zest for garnish
Instructions
Prep. Preheat your oven to 325°F with a baking rack in the center. Grease your 13x9-inch pan with non-stick spray.
Mix Dry Ingredients. In a medium bowl, whisk together the flour, salt, baking powder, and baking soda.
Beat Eggs & Sugar. In your stand mixer bowl or another large mixing bowl, beat the eggs and sugar at medium-high speed for 2–3 minutes until the mixture is very light and fluffy.
Add Sourdough Starter. Gently mix in the sourdough discard until just combined.
Combine Dry & Wet. Add the dry ingredients to the egg mixture and beat until just incorporated—scraping down the sides if needed.
Heat the Milk Mixture. In a small saucepan, heat the milk with the vegetable oil and butter until it's just beginning to simmer. Remove from the heat.
Fold In Milk & Lemon. Gently fold the warm milk mixture into the batter. Then, stir in the lemon juice, lemon zest, and food coloring if using.
Bake. Pour the batter into your prepared pan and bake for 30-35 minutes. (The cake might look a bit spongy—that's normal.) Test with a toothpick; it should come out clean.
Cool. Allow the cake to cool completely in the pan before frosting.
Make the Lemon Buttercream. Beat the butter, powdered sugar, lemon zest, lemon juice, salt, and 1 tablespoon heavy cream in your stand mixer. Add a bit more cream if needed until you reach your desired frosting consistency.
Assemble. Spread the buttercream evenly over the cake. Top with thin lemon slices or lemon zest curls. Serve straight from the pan, and store any leftovers in an airtight container in the fridge.
Video
Notes
You can bake the cake a day ahead and frost it just before serving.