Lemon-Cheese Layer Cake

Prepare the Cake Layers: Preheat oven to 375°F with racks in middle and lower third positions. Coat 4 (8-inch) round cake pans with cooking spray, and line with parchment paper; set aside. Beat butter with a stand mixer fitted with a paddle attachment on medium speed until creamy, about 1 minute. Gradually add granulated sugar, beating until light and fluffy, 3 to 4 minutes. Stop mixer; scrape down sides. With mixer running on low speed, add egg whites, 1 at a time, stopping to scrape down sides as needed. Add vanilla and lemon zest; beat until just combined, about 30 seconds.

Whisk together cake flour, baking powder, and salt in a medium bowl. Add to butter mixture alternately with milk, beginning and ending with flour mixture, beating on low speed until just combined after each addition. Spread about ⅔ cup of batter into each of the prepared pans. 

Bake cakes in preheated oven until a wooden pick inserted in center of cakes comes out clean, about 12 minutes. Cool in pans on wire racks 5 minutes. Remove cakes from pans; place directly on wire racks to cool completely, about 30 minutes. Meanwhile, coat pans again with cooking spray, and line again with parchment. Divide remaining batter evenly among pans (about ⅔ cup of batter per pan). Bake cakes per previous instructions. (Cake Layers can be chilled overnight; separate the layers with plastic wrap.)

While cakes are cooling, prepare the Lemon Curd Filling: Whisk together egg yolks, granulated sugar, cornstarch, lemon zest and juice, and salt in a medium-size heavy saucepan until combined. Cook mixture over medium, stirring constantly with a wooden spoon, until mixture is thick and coats the back of spoon, 8 to 10 minutes. Remove from heat. Add cold butter; stir until melted and smooth.

Pour mixture through a fine mesh strainer into a medium bowl; discard any lumps. Place bowl with strained Lemon Curd Filling into a large bowl filled with ice water. Let stand, stirring often, until mixture is cool, about 20 minutes. Remove medium bowl from ice water bowl, and place a piece of plastic wrap directly on top of filling (to prevent a film from forming). Cover and chill until filling is firm, at least 4 hours or up to 3 days.

Prepare the Lemon Buttercream: Beat butter with an electric mixer on medium speed until creamy, about 1 minute. Gradually add powdered sugar, beating on low speed until combined, about 1 minute. Add lemon zest and vanilla, beating until just combined, about 10 seconds. With mixer running on medium speed, gradually add cream, beating until fluffy and spreadable, about 30 seconds. 

Assemble the cake: Place 1 Cake Layer on a serving platter or a cake stand. Spoon ¼ cup Lemon Curd Filling onto cake; spread evenly to edges using an offset spatula. Repeat process with 6 more Cake Layers and Lemon Curd Filling. Top with remaining Cake Layer. (You should have about 1¼ cups filling remaining. Place in a piping bag or ziplock plastic bag; chill until ready to use.) Chill cake, uncovered, 1 hour. 

Spread Lemon Buttercream over top and sides of cake. Snip a ½-inch tip off piping bag. Pipe dots of reserved Lemon Curd Filling, about the size of a quarter, around the top of cake to create a ring, leaving about a 1-inch border around edge. Using an offset spatula, drag dots of filling toward center of cake to create a flowerlike pattern.