HOW TO MAKE RAINBOW FROSTING FOR CAKE RECIPES

Steps:

• Heat oven to 350°F. Grease and flour 2 (8-inch) round cake pans or spray with baking spray. Set aside.
• Combine flour, baking powder and 1/4 teaspoon salt in bowl; set aside.
• Beat sugar and 1 cup butter in another bowl at medium speed, scraping bowl occasionally, until creamy. Add eggs, 1 at a time, beating well after each addition. Add 1 tablespoon vanilla; mix well. Add flour mixture alternately with milk, beating at low speed after each addition, just until mixed.
• Divide batter evenly among 6 bowls with about 3/4 cup each. Tint cake batters red, orange, yellow, green, blue and purple. Spread red and orange batter into prepared pans. Bake 8-10 minutes or until toothpick inserted into center comes out clean. Cool 3 minutes; remove from pans to cooling rack. Cool completely. Meanwhile, wash pans; grease and flour pans. Repeat with remaining colors until all cake layers are baked.
• Beat 2 cups butter in medium bowl at medium speed until creamy. Gradually add powdered sugar and 1/4 teaspoon salt alternatley with whipping cream and 1 tablespoon vanilla, beating at low speed until well incorporated. Beat at medium speed until smooth and creamy. Remove 2 cups frosting; set aside. Divide remaining frosting evenly among 6 bowls with about 1/3 cup each. Tint frostings red, orange, yellow, green, blue and purple. Set aside.
• Place purple cake layer onto serving plate, bottom-side up. Frost top with 1/4 cup white frosting. Place blue cake layer over frosting; frost with 1/4 cup white frosting. Continuing adding green, yellow, orange and red layers in that order, frosting with 1/4 cup white frosting between each layer. Frost outside of cake with remaining white frosting. This layer of frosting will be thin and cake will be visible through frosting. Once frosted, refrigerate cake 30 minutes. (This is called a crumb coat and will prevent crumbs from interfering when piping rosettes.)
• Place each tinted frosting into individual resealable plastic food bag; push frosting to one corner. Cut off 1/2 inch from tip of corner. Place 18-inch-long piece of plastic food wrap onto counter surface. Pipe each color onto plastic wrap to form wide 12-inch horizontal lines (using all of frosting) that are touching.
• Gently roll frosting lines into one large log using plastic wrap. Snip tip off one end of plastic wrap. Place cut-side down into piping bag fitted with size 1M open-star tip. Pipe rainbow rosettes onto cake beginning with middle of top of cake and working out and down sides so the most vibrant colors are on top of cake.

Steps:

• Preheat the oven to 400 degrees F (200 degrees C). Grease six 9-inch round cake pans and dust with flour.
• Sift together the flour, baking powder, and baking soda.
• Beat 3/4 cup plus 2 tablespoons butter, milk, sugar, egg whites, and vanilla extract in a large bowl with an electric mixer until smooth. Stir in flour mixture and mix until just combined.
• Divide cake batter evenly between 6 bowls. Mix in different food coloring to each bowl, creating 6 different colored batters. Start with just 1 to 2 drops of food coloring in each bowl, then mix; you can always add more.
• Bake each cake in the preheated oven, until a toothpick inserted in the center comes out clean, 15 to 20 minutes. Set aside to cool.
• Beat cream in a chilled glass or metal bowl with an electric mixer until stiff peaks form. Stir together confectioners' sugar and mascarpone cheese in a separate bowl, then fold gently into the whipped cream until smooth.
• Spread frosting on each layer of cooled cake, placing one on top of the other. Cover the top and sides with the remaining frosting. Refrigerate for 2 hours before serving.