BLUE BUTTERCREAM 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 375 degrees F. Spray the bottom and sides of six 8-inch round cake pans; dust with flour and tap out excess.
• Whisk together the flour, baking powder and salt in a medium bowl; set aside.
• Beat the butter, sugar and oil in a large bowl with an electric mixer on medium-high speed until light in color and fluffy, about 5 minutes. Beat in the eggs, one at a time, then the vanilla seeds, until combined.
• Transfer the creamed mixture to a very large mixing bowl, then alternate folding in the flour mixture and the milk with a spatula, adding the flour in 3 additions and the milk in 2, starting and ending with the flour, just until smooth. Divide the batter equally among 6 mixing bowls. Using gel food colors, tint each bowl with one of the colors of the rainbow. Pour each color into its own prepared cake pan.
• Bake, rotating the pans halfway through, until a toothpick inserted in the centers comes out clean, 18 to 20 minutes. Cool the cakes in the pans on a rack for 10 minutes, then remove the cakes to the rack to cool completely.
• Level the tops of any cake layers that have domed by slicing the domes off with a serrated knife. Put some buttercream into a pastry bag fitted with a large round tip. Put the bottom cake layer onto a cake plate. Pipe around the edge of the cake layer to create a frosting "dam." Fill the center with a thin layer of jam (about 1/2 cup). Top with another cake layer and repeat until you have stacked and filled all the layers. Frost the outside of the cake with the remaining buttercream and decorate as desired.
• In the bowl of a stand mixer, combine the confectioners' sugar, butter, milk, vanilla seeds and salt. Beat on low speed for a while. When the sugar is incorporated, turn the speed up and beat until the buttercream is fluffy and smooth. If it's too wet, add a bit more confectioners' sugar. If it's too stiff, add a bit more butter. Be sure to scrape the sides of the bowl once or twice to make sure everything is combined.
• Use immediately or store in an airtight container at room temperature for up to 24 hours or in the fridge for up to 2 weeks. Rewhip cold buttercream before using.