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American Flag Cake

American flag cake made as a patriotic sheet cake: two baked white cake layers are cooled completely, then covered in thick white buttercream and topped with a blueberry canton, strawberry red stripes, and banana or extra frosting white stripes. The finished dessert has a clean, vivid flag design that stays crisp for easy slicing.
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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: 520
Ingredients Equipment Method Notes

Ingredients
  

White cake mix
  • 2 boxes white cake mix Plus ingredients listed on the box.
Frosting
  • 2 cup unsalted butter Softened.
  • 6 cup powdered sugar
  • 2 tsp vanilla extract
  • 5 tbsp heavy cream Use 4–6 tbsp to reach a spreadable consistency.
Decoration
  • 2 cup fresh blueberries
  • 2 lb fresh strawberries Hulled and sliced lengthwise.
  • 1 cup banana slices Or use extra white frosting for the white stripes.

Equipment

  • 1 sheet pan

Method
 

Bake and cool the cake
  1. Heat the oven and bake both white cake mixes in a large 12x18 sheet pan (or two 9x13 pans joined together) according to package directions. Bake until a toothpick inserted in the center comes out clean, then cool the cake completely.
Make the buttercream
  1. Beat the softened unsalted butter until fluffy, using an electric mixer at a medium speed. Continue beating while gradually adding powdered sugar until fully incorporated.
  2. Add the vanilla extract and 4–6 tablespoons heavy cream, then beat until smooth and spreadable. Stop and scrape the bowl as needed so the frosting has an even texture.
Frost and decorate like a flag
  1. Spread a thick, even layer of white buttercream over the entire top of the cooled sheet cake. Use a flat spatula to smooth the surface so the fruit pattern looks crisp.
  2. In the upper left corner, arrange fresh blueberries into a dense rectangle to form the canton. Press them lightly into the frosting so they stay in place.
  3. Create red stripes by arranging rows of sliced fresh strawberries flat across the length of the cake. Keep the rows uniform and consistent in spacing from edge to edge.
  4. Fill the white stripes by piping extra frosting in rows between the strawberry rows or placing thin banana slices. Aim for clean lines so the flag design looks vivid from overhead.
Chill and serve
  1. Refrigerate the decorated cake until ready to serve, allowing the frosting to firm up. Chill for about 1 hour, then slice into squares.

Notes

For the cleanest flag lines, fully cool the cake before frosting so the buttercream doesn’t melt or slide. Refrigerate leftovers in an airtight container for up to 3 days; freezing is not recommended because fresh strawberries and blueberries can soften. If you want an easy swap, use all extra white frosting instead of banana slices for the white stripes so the top stays uniform and dairy-only.