01 -
Heat your oven to 350°F. Line the bottoms of three 8-inch cake pans with parchment paper and grease the sides. Get your bake-even strips ready if you have them.
02 -
In a large bowl, mix sugar, oil, eggs, and lemon extract. Beat for about 2 minutes until the mixture lightens in color. Scrape down the sides as needed.
03 -
Zest 2 lemons into your batter, then squeeze them to get 1/4 cup juice. Add the zest, juice, and sour cream to your mixture and beat until well combined.
04 -
Mix your flour, baking powder, and salt in a separate bowl. Add half to your batter while pouring in half the buttermilk. Mix just until the flour starts to blend in.
05 -
Add the remaining dry ingredients and buttermilk, beating until everything combines nicely. Scrape the bowl to make sure it's all mixed properly.
06 -
Toss your blueberries with 2 tablespoons of flour, then gently fold most of them into the batter. Save a small handful for topping.
07 -
Divide the batter between your three pans (about 1 2/3 cups per pan). Sprinkle the remaining blueberries on top. Bake for 20-23 minutes, rotating pans halfway through. They're done when a toothpick comes out clean.
08 -
While cakes cool, chill your mixing bowl and whisk attachment in the freezer for 5-10 minutes.
09 -
Put cold mascarpone in your chilled bowl and beat on medium-low. Slowly pour in the cream until mascarpone turns liquid. Increase to high speed and beat to soft peaks. Add powdered sugar and vanilla, mix on low, then beat on high until stiff peaks form.
10 -
Level off the cake tops if needed. Put some frosting on your cake board and place the first layer on top. Pipe a layer of frosting and spread evenly, then add half the lemon curd on top of that.
11 -
Add the second cake layer and repeat with frosting and remaining lemon curd. Add the final layer on top. Use frosting to fill gaps between layers and create a crumb coat.
12 -
Frost the top and sides completely. Smooth with an icing tool, then add texture if desired. Pipe decorative swirls on top and garnish with lemon slices and extra blueberries. Keep refrigerated.