Life-of-the-Party Layer Cake

Preparation

1. Cake

   Step 1

   Place a rack in middle of oven; preheat to 350°. Lightly coat pans with nonstick spray. Line bottom of each pan with a parchment paper round. Lightly coat parchment with nonstick spray. Whisk flour, baking powder, and salt in a medium bowl. Using an electric mixer on medium speed, beat sugar and butter in a large bowl, scraping down sides of bowl as needed, until pale and fluffy, about 3 minutes. Add eggs one at a time, beating well and scraping down sides of bowl after each addition.

   Step 2

   Combine milk and vanilla in a measuring glass. Reduce speed to low; beat in dry ingredients in 3 additions, alternating with milk mixture in 2 additions, mixing well after each addition. Divide batter evenly among 6 small bowls (if using a scale, about 200 g each).

   Step 3

   Color batter in each bowl with orange, green, yellow, red, pink, and black food coloring, adding and stirring in until you reach desired hue. Scrape a color of batter into each prepared pan; smooth surface. Bake cakes, rotating pans halfway through if browning too much in one spot, until tops spring back when very gently pressed and a tester inserted in the center comes out clean (go all the way to the bottom), 16–20 minutes. Transfer pans to wire racks and let cakes cool in pans 10 minutes. Run a small knife or offset spatula around inside of pans to loosen cakes, then turn out onto racks. Remove parchment and let cool completely (keep upside down).

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2. Frosting and Assembly

   Step 4

   Using clean beaters, beat butter on medium speed in a large bowl until smooth. Add cream cheese a few pieces at a time, beating until smooth. Beat in vanilla, then reduce speed to low and add powdered sugar a little at a time, beating until smooth. Mix in lemon juice and salt. Scoop 1 cup frosting into a small bowl; set aside. Add a few drops yellow food coloring to frosting in large bowl and stir well; add more until you reach desired hue.

   Step 5

   Turn cakes over. Using ring cutter, punch out a hole in center of each cake except orange cake. Place half of yellow frosting in piping bag (a resealable bag with a corner cut off also will work). Pipe a circle of frosting onto a plate or cake stand. Place black cake on top and pipe several rings of frosting on top of cake. Stack pink cake on top, lining up center holes, and pipe several rings of frosting on top. Repeat with red, yellow, and green cakes. 

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   Step 6

   Add desired fillings to center of cake. Place orange cake on top to close. Frost outside of cake in an even layer. (It doesn’t need to be perfect; this is just to trap all the loose bits of cake so the next layer will be more even.) Chill, uncovered, until frosting is firm, about 1 hour.

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   Step 7

   Coat cake in another layer of frosting, taking your time to make it even. If the frosting isn’t firm, chill another 30 minutes (important when you add the other colors). Divide reserved 1 cup frosting among 4 small bowls and add orange, green, red, and black food coloring to reach desired hue. Place dollops of each color of frosting all over cake. Run scraper around cake in one continuous motion to create smooth streaks of color.

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   Do ahead: Cake can be made 1 day ahead. Chill, uncovered.