I made only five layers. I divided the first box of batter into four 9-inch cakes. I divided the second box of batter, too, using one quarter for the last color of cake, and using the rest to make rainbow cupcakes. To color the batter, I used Americolor Soft Gel Pastes, Red Red, Egg Yellow, Electric Green, Sky Blue and Regal Purple. I needed two batches of buttercream frosting.
For the cupcakes, I removed them from the freezer, unwrapped them and let them thaw completely at room temperature before frosting with a disposable decorating bag and star tip. I also keep my cupcakes in the fridge the night before a party.
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