Triple-Lemon Blueberry Layer Cake
Ingredients
For the Cake:
  • 2 cups plus 6 tablespoons 290 g all-purpose flour, sifted
  • 2 teaspoons 9 g baking powder
  • 1 teaspoon 7g salt
  • 3 cups fresh blueberries
  • 1/2 cup 120 ml sour cream
  • 1/2 cup 120 ml whole milk
  • 2 teaspoons 10 ml pure vanilla extract
  • 1/2 teaspoon 2.5 ml pure lemon extract
  • 1 teaspoon 5 ml lemon zest
  • 1 cup 2 sticks(227 g) unsalted butter, softened
  • 1-1/2 cups 300 g white sugar
  • 4 large eggs at room temperature
For the Frosting:
  • 1 cup 2 sticks(227 g) unsalted butter, softened
  • 2 teaspoons 10 ml lemon zest
  • 5 cups 625 g icing sugar, sifted
  • 2 tablespoons 30 ml fresh lemon juice
  • 1/4 cup 60 ml whipping cream (35% cream)
  • 1/4 teaspoon 1.25 pure lemon extract
  • a pinch of salt
  • yellow food gel optional
Instructions
For the Cake:
  1. Preheat oven to 350°F. Prepare three 8" round cake pans with parchment paper, butter and flour. Sift dry ingredients into medium bowl. Transfer 1 tablespoon flour mixture to larger bowl. Add fresh blueberries and toss to coat them with flour. Set remaining flour mixture and blueberries aside.
  2. Stir sour cream, whole milk, vanilla extract, lemon extract and lemon zest in small bowl.
  3. In the bowl of a stand mixer, cream butter and sugar, until pale yellow and very fluffy, about 5 minutes. Beat in eggs one at a time, until well combined.
  4. Mix in flour mixture alternately with milk mixture, starting and ending with flour mixture. Stir until just combined. Gently fold in blueberries.
  5. Divide batter equally among prepared pans. Bake cakes until toothpick inserted into center comes out clean, about 25 minutes. Cool cakes in pans on racks for about 10 minutes, then invert onto racks until completely cool.
For the Frosting:
  1. Cream butter and lemon zest in bowl of electric mixer fitted with paddle attachment, about 3 minutes. Slowly add icing sugar, mixing on low speed for about 2 minutes.
  2. Add remaining ingredients and beat on med-high for 3-4 minutes until very fluffy. If using color gel, add a drop or two (really, no more than that, because too much sunshine really can be a bad thing!), then beat until blended.
Assembly of the Triple-Lemon Blueberry Layer Cake:
  1. Spread thin dollop of frosting on an 8-inch thin cake board or cake plate. Transfer 1 cake layer to board, face up.
  2. Create a dam around the perimeter of the layer using frosting in a pastry bag fitted with a coupler, then spread lemon curd (apprx 1 cup) inside the dam--this prevents the curd from reaching out over edges.
  3. Top with second layer, face-up; repeat frosting around perimeter and lemon curd filling.
  4. Top with third cake layer, face-down (brown smooth side up). Spread thin layer (crumb coat) of over top and sides of cake, using offset palette knife and bench scraper for smooth finish. Place cake in refrigerator for about 30 mins to chill.
  5. from refrigerator and using same method, frost cake with generous layer of frosting, smoothing again. For ruffled border, add frosting to piping bag with petal tip (Wilton #123), and with skinny end facing out, use back and forth/up and down motion to create short ruffles.
Sweetapolita's Notes

Due to the lemon curd filling, keep cake covered and refrigerated (for up to 2 days) but serve at room temperature.