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American Flag Cake

American flag cake made as a patriotic sheet cake with a thick white buttercream layer and a clean blueberry canton with strawberry red stripes. Decorate a fully cooled sheet cake for vivid, uniform red-white-blue fruit rows perfect for Independence Day.
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Prep Time 45 minutes
Cook Time 35 minutes
cooling 1 hour
Total Time 2 hours 20 minutes
Servings: 20 servings
Course: Dessert
Cuisine: American
Calories: 470
Ingredients Equipment Method Notes

Ingredients
  

White cake layers
  • 2 boxes white cake mix Use the ingredients listed on the box (eggs, water, and oil/butter), since package directions vary by brand.
White buttercream frosting
  • 2 cups unsalted butter Soften to room temperature.
  • 6 cups powdered sugar
  • 2 tsp vanilla extract
  • 5 tbsp heavy cream Use 4–6 tbsp to reach spreadable consistency.
Flag decoration
  • 2 cup fresh blueberries
  • 2 lb fresh strawberries Hull and slice lengthwise into thin long pieces.
  • 1 banana slices Use banana slices for the white stripes, or skip and use extra frosting if preferred.

Equipment

  • 1 sheet pan

Method
 

Bake and cool the sheet cake
  1. Bake both white cake mixes in a large 12x18 sheet pan or two 9x13 pans according to package directions until a toothpick comes out clean, then cool completely.
  2. Cool the baked cakes fully before frosting so the buttercream stays smooth and the fruit decorations don’t slide.
Make the white buttercream
  1. Beat softened unsalted butter until fluffy, then gradually add powdered sugar, beating until combined.
  2. Add vanilla extract and heavy cream (4–6 tbsp as needed) and beat until smooth and spreadable.
Frost and decorate the American flag
  1. Frost the entire top of the cooled sheet cake with a thick, even layer of white buttercream.
  2. In the upper left corner, arrange fresh blueberries in a dense rectangle to form the canton.
  3. Create the red stripes by arranging rows of sliced strawberries flat across the length of the cake.
  4. Fill the white stripes by piping extra frosting in rows between the strawberry rows or placing thin banana slices.
Chill and serve
  1. Refrigerate the decorated cake until ready to serve, keeping the fruit firm and the stripes set.
  2. Slice into squares and serve cold.

Notes

Pro tip: cool the cake completely and frost while it’s fully firm—warm cake can cause the blueberry/strawberry rows to sink. Store covered in the refrigerator for up to 3 days; freeze undecorated cake layers for up to 2 months (thaw overnight in the fridge, then frost and decorate). For a lighter swap, use half the powdered sugar for a less-sweet frosting only if you thicken with an extra splash of cream to keep it spreadable.