Rectangle Rainbow Buttercream Cake

Ingredients:

For the Cake:

• Your preferred cake recipe or mix (enough for a rectangular cake pan)
• Ingredients required for the cake mix (e.g., eggs, oil, water)

For the Rainbow Buttercream:

• 1 cup unsalted butter, softened
• 4 cups powdered sugar
• 1/4 cup whole milk or cream
• 1 teaspoon vanilla extract
• Gel food coloring (red, orange, yellow, green, blue, purple)

Steps:

Cake:

Step 1: Preheat your oven according to the cake recipe or mix instructions.

Step 2: Prepare your rectangular cake pan by greasing and flouring it.

Step 3: Prepare the cake batter according to the recipe or mix instructions.

Step 4: Pour the batter into the rectangular cake pan.

Step 5: Bake the cake in the preheated oven until a toothpick inserted into the center comes out clean. Follow the recommended baking time and temperature from your recipe or mix.

Step 6: Allow the cake to cool completely before frosting.

Rainbow Buttercream:

Step 7: In a large bowl, beat softened butter until creamy.

Step 8: Gradually add powdered sugar, alternating with milk or cream, and continue to beat until smooth and fluffy.

Step 9: Add vanilla extract and mix until well combined.

Step 10: Divide the buttercream into six equal portions.

Step 11: Using gel food coloring, tint each portion with a different color of the rainbow (red, orange, yellow, green, blue, purple).

Assembly:

Step 12: Once the cake is completely cooled, carefully remove it from the pan.

Step 13: Level the top of the cake if needed.

Step 14: Begin by spreading a thin layer of one colored buttercream on the top of the cake.

Step 15: Continue stacking and frosting each layer with a different colored buttercream, creating a rainbow pattern.

Step 16: Frost the sides and top of the entire cake with the remaining buttercream.

Step 17: Optionally, smooth the buttercream with a cake scraper for a polished finish.

Step 18: Decorate the top with additional rainbow patterns or decorations if desired.

Serve and enjoy this Rectangle Rainbow Buttercream Cake as a delightful and visually stunning centerpiece for your celebration.