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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 evenly spaced strawberry red stripes. This white cake with fruit is assembled after fully cooling for firm, sliceable squares.
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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 box white cake mix Use the mix plus the ingredients called for on the box (eggs, water, and oil/butter).
frosting
  • 2 cup unsalted butter Soften until spreadable.
  • 6 cup powdered sugar
  • 2 tsp vanilla extract
  • 5 tbsp heavy cream Use 4–6 tbsp to reach spreadable thickness.
decoration
  • 2 cup fresh blueberries
  • 2 lb fresh strawberries Hulled and sliced lengthwise into thin, flat pieces.
  • 1 banana slices Optional for white stripes; use extra white frosting instead if preferred.

Equipment

  • 1 sheet pan

Method
 

Bake the sheet cake
  1. Heat the oven and bake both cake mixes in a large 12x18 sheet pan or two 9x13 pans joined together according to package directions, then remove and cool completely.
  2. Confirm the cakes are fully cool before frosting to prevent the buttercream from melting.
Make the white buttercream frosting
  1. Beat the softened unsalted butter until fluffy, about 1–2 minutes, then gradually add powdered sugar while mixing.
  2. Add vanilla extract and 4–6 tablespoons heavy cream, then beat until smooth and spreadable, stopping to scrape the bowl as needed.
Frost and decorate the 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 into a dense rectangle to form the canton.
  3. Create red stripes by arranging rows of sliced fresh strawberries flat across the length of the cake.
  4. Fill the white stripes by piping extra frosting in rows between the strawberry rows, or by placing thin banana slices for the white sections.
Chill and serve
  1. Refrigerate the assembled American flag cake until ready to serve, at least 1 hour, for clean slicing and firm fruit placement.
  2. Slice into squares and serve chilled.

Notes

Pro tip: cool the cake completely before frosting, then chill briefly after decorating so the stripes set. Store covered in the refrigerator for up to 3 days; freezing is not recommended because fresh fruit can weep and soften. For a lower-sugar option, replace part of the powdered sugar with an equal-amount blend from a 1:1 baking substitute designed for buttercream (check package directions).