- 1 (15.25oz). box vanilla cake, plus ingredients called for on box
- Juice and zest of 1 1/2 lemons, divided, plus more zest for garnish
- 1 3/4 c. fresh blueberries, divided
- 3 tbsp. all-purpose flour
- 1 c. (2 sticks) butter, softened
- 3 c. powdered sugar
- 1/4 c. heavy cream
- 1 tsp. pure vanilla extract
- Pinch of kosher salt
- 2 Thin lemon slices, for topping
- Preheat oven to 350º and grease three 9″ cake pans with cooking spray. Line with parchment. Prepare cake mix according to package directions, then stir in juice and zest of 1 lemon.
- In a small bowl, toss 1 cup blueberries and flour until completely coated (to keep the berries from sinking). Gently fold blueberries into the batter.
- Divide cake batter evenly among prepared cake pans and bake until a toothpick comes out clean, 18 to 20 minutes.
- Let cool in pans for 10 minutes, then invert onto a wire rack and let cool completely.
- Make frosting: In a large bowl using a hand mixer or the bowl of a stand mixer using the whisk attachment, beat butter and 2 1/2 cups powdered sugar. Add remaining lemon juice and zest and heavy cream and beat until combined, then beat in vanilla and salt. (Add remaining 1/2 cup powdered sugar as desired for texture and flavor.)
- Place a dab of frosting on cake plate (to keep cake in place) and place parchment strips on each side of the cake plate. Place down first cake and top with frosting, then top with second cake and frost. Repeat with third cake and frost sides.
- Garnish with remaining blueberries, lemon slices, and zest and serve.