Rainbow Sheet Cake: A Bright, Colorful, and Crowd-Pleasing
Rainbow Sheet Cake is a colorful vanilla cake featuring vibrant rainbow swirls or layers baked into a single sheet pan and topped with creamy buttercream frosting. Easy to prepare and perfect for serving a crowd, this festive dessert is ideal for birthdays, celebrations, and special occasions. Its soft texture, rich vanilla flavor, and cheerful colors make it a guaranteed crowd-pleaser. Every slice reveals a beautiful rainbow surprise that brings smiles to both children and adults.
Ingredients
For the Cake
- 3 cups all-purpose flour
- 2½ teaspoons baking powder
- ½ teaspoon salt
- 1 cup unsalted butter, softened
- 2 cups granulated sugar
- 4 large eggs
- 1 tablespoon vanilla extract
- 1½ cups whole milk
For the Buttercream Frosting
- 1½ cups unsalted butter, softened
- 5 cups powdered sugar
- 3 tablespoons heavy cream
- 2 teaspoons vanilla extract
- Pinch of salt
Instructions
- Preheat oven to 350°F (175°C).Grease a 9x13-inch sheet cake pan and line with parchment paper.
- In a bowl, whisk together flour, baking powder, and salt.In a large mixing bowl, beat butter and sugar until light and fluffy.Add eggs one at a time, mixing well after each addition.Add vanilla extract.Alternately add dry ingredients and milk until a smooth batter forms.
- Divide the batter evenly into six bowls.
- Drop spoonfuls of each colored batter randomly throughout the prepared pan.Use all six colors until the pan is evenly filled.Gently swirl with a skewer or knife to create a rainbow marble effect.
- Bake for 28–32 minutes or until a toothpick inserted in the center comes out clean.Allow the cake to cool completely.
- Beat butter until creamy.Gradually add powdered sugar.Add vanilla extract, cream, and salt.Beat until light and fluffy.
- Spread frosting evenly over the cooled cake.Decorate with rainbow sprinkles, candy decorations, or edible glitter
- Slice into squares and enjoy the colorful rainbow interior.
Notes
- Gel food coloring produces the most vibrant colors.
- Avoid overmixing after coloring the batter.
- Allow the cake to cool fully before frosting.
- Use room-temperature ingredients for best results.
- A crumb coat is unnecessary for sheet cakes.
- Store covered to maintain freshness.
- Decorate immediately after frosting.
- Use high-quality vanilla extract for the best flavor.