Lemon Meringue Layer Cake
From America’s Test Kitchen Best Ever Desserts Cookbook
Lemon Curd Filling
Meringue Frosting
For Lemon Curd filling
  1. Sprinkle gelatin over 1 TB lemon juice in small bowl; set aside. Heat sugar, salt, and remaining lemon juice in medium saucepan over medium-high heat, stirring occasionally, until sugar dissolves and mixture is hot but not boiling. Whisk eggs and yolks together in large bowl. Whisking constantly, slowly pour hot lemon-sugar mixture into eggs, then return mixture to saucepan. Cook over medium-low heat, stirring constantly with heat resistant spatula, until mixture registers 170 degrees and is thick enough to leave trail when spatula is scraped along saucepan bottom, 4-6 minutes (but trust the temperature more than the time!) Immediately remove saucepan from heat and stir in gelatin mixture until dissolved. Stir in butter until incorporated. Pour filling through fine-mesh strainer into bowl (you should have about 3 cups). Place plastic wrap directly on surface of filling and refrigerate until firm enough to spread, at least 4 hours.
For cake
  1. Adjust oven rack to middle position and heat oven to 350 degrees. Grease two 9-inch round cake pans, line with parchment paper, grease parchment, and flour pans. Whisk milk, egg whites, and vanilla together in 4-cup liquid measuring cup.
  2. Using stand mixer fitted with paddle, mix flour, sugar, baking powder and salt on low speed until combined. Add butter, 1 piece at a time, and mix until only pea-size pieces remain, about 1 minute. Add all but 1/2 cup milk mixture, increase speed to medium-high, and beat until light and fluffy, about 1 minute. Reduce speed to medium-low, add remaining 1/2 cup milk mixture, and beat until incorporated, about 30 seconds. Give batter final stir by hand.
  3. Divide batter evenly between prepared pans and smooth tops with rubber spatula. Bake until toothpick inserted in center comes out clean, 23 to 25 minutes, rotating pans halfway through baking. Let cakes cool in pans on wire rack for 10 minutes. Remove cakes from pans, discarding parchment, and let cool completely on rack, about 2 hours.
  4. Using long serrated knife, cut 1 horizontal line around sides of each layer; then, following scored lines, cut each layer into 2 even layers.
  5. Place 1 cake layer on platter. Spread 1 cup lemon curd evenly over top, leaving 1/2 inch border around edge. Repeat with 2 more cake layers, pressing lightly to adhere and spreading each layer with 1 cup curd. Top with remaining cake layer, press lightly to adhere, and smooth out any filling that has leaked from sides of cake.
For meringue frosting
  1. Combine all ingredients in bowl of stand mixer and set bowl over medium saucepan filled with 1 inch barely simmering water, making sure that water does not touch bottom of bowl (basically you are making a double boiler with your stand mixer bowl). Whisk constantly until mixture registers 160 degrees, 5 to 10 minutes. Remove bowl from heat. Fit stand mixer with whisk and whip mixture on medium speed until soft peaks form, about 5 minutes. Increase speed to medium-high and continue to whip until mixture has cooled completely and stiff peaks form, about 5 minutes longer.
  2. Spread about 1 cup frosting evenly over top, right to edge of cake. Spread remaining frosting evenly over sides of cake. Use offset spatula to smooth frosting.