Lemon-Coconut Cake With Mascarpone Frosting


1 1/3 c. unsalted butter, softened, plus more for the pans
4 c. cake flour, plus more for the pans
1 1/3 cups whole milk
2 tsp. pure vanilla extract
4 tsp. baking powder
1 tsp. fine salt
2 2/3 c. granulated sugar
7 large egg whites, at room temperature
Lemon-Coconut Filling
1 c. sweetened flaked coconut, packed
2/3 c. store-bought lemon curd (such as Dickinson's)
1/4 c. sour cream
1 tbsp. lemon zest
Creamy Mascarpone Frosting
8 oz. mascarpone cheese
1 1/2 c. heavy cream
2 tsp. coconut extract
1/3 c. granulated sugar


Preheat oven to 350°F. Butter and flour three 9-inch cake pans; line bottoms with parchment paper. Stir together milk and vanilla in a bowl. Sift together flour, baking powder, and salt in another bowl.
Beat butter on medium speed with an electric mixer until light and fluffy, 2 to 3 minutes. Gradually beat in sugar until light and fluffy, 1 to 2 minutes. Reduce mixer speed to low, add flour mixture alternately with milk mixture, beginning and ending with flour mixture, beating just until blended after each addition.
Beat egg whites, in a clean dry bowl, at medium speed with an electric mixer until stiff peaks form, 2 to 3 minutes. Gently fold egg whites, in three additions, into batter. Transfer batter to prepared pans.
Bake until a toothpick inserted in center comes out clean, 25 to 28 minutes. Cool in pans on wire racks 10 minutes. Invert onto wire racks; carefully peel off and discard parchment paper. Cool completely.
Place one cake layer on a cake stand or serving plate and spread top with half of the Lemon-Coconut Filling (leaving a ¼-inch border all around). Top with a second cake layer and top with the remaining Lemon-Coconut Filling (leaving a ¼-inch border all around); top with the remaining cake layer. Frost top and sides with Creamy Mascarpone Frosting. Decorate with fondant daisies.
To make Lemon-Coconut Filling, stir together 1 packed cup sweetened flaked coconut, ? cup store-bought lemon curd (such as Dickinson's), ¼ cup sour cream, 1 tablespoon lemon zest. Cover and chill until ready to use.
To make Creamy Mascarpone Frosting, stir softened mascarpone cheese in a bowl until smooth. Beat 1 ½ cups heavy cream, 2 teaspoons pure vanilla extract, and ¼ teaspoon coconut extract on low speed with an electric mixer until foamy, 1 to 2 minutes. Increase speed to medium-high, and gradually add ? cup granulated sugar, beating just until stiff peaks form, 2 to 3 minutes. Gently fold whipped cream mixture into mascarpone cheese. Use immediately.