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American Flag Cake

American flag cake with a full-sheet white frosted base and a crisp blueberry canton with uniform strawberry red stripes. Built like a patriotic sheet cake—layered fruit rows and clean piping for a vivid red, white, and blue look.
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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: 420
Ingredients Equipment Method Notes

Ingredients
  

White cake
  • 2 box white cake mix Use the ingredients listed on the boxes (eggs, oil, water) when preparing.
Buttercream frosting
  • 2 cup unsalted butter Softened.
  • 6 cup powdered sugar
  • 2 tsp vanilla extract
  • 4 tbsp heavy cream Add 4–6 tbsp as needed for a spreadable consistency.
Fruit decoration
  • 2 cup fresh blueberries Keep dry for clean placement.
  • 2 lb fresh strawberries Hulled and sliced lengthwise.
  • 1 banana slices Optional: use thin banana slices for white stripes, or use extra white frosting instead.

Equipment

  • 1 sheet pan

Method
 

Bake the sheet cakes
  1. Preheat the oven and bake both white cake mixes in a large 12x18 sheet pan or two 9x13 pans joined together according to package directions, using a single level bake for even top surfaces. Bake for the package time until a toothpick inserted in the center comes out clean, then cool completely.
Make the buttercream
  1. Beat softened unsalted butter until fluffy, about 1–2 minutes, then gradually add powdered sugar while mixing on low. Add vanilla extract and heavy cream (use 4–6 tbsp total) and beat until smooth and spreadable, scraping the bowl as needed.
Frost the cake
  1. Spread a thick, even layer of white buttercream over the entire top of the cooled sheet cake, smoothing the surface so the fruit stripes sit flat. Chill the cake briefly if the frosting is too soft to work with.
Arrange the American flag design
  1. In the upper left corner, arrange fresh blueberries into a dense rectangle for the blueberry canton, pressing gently so the pieces touch. Aim for precise edges for a clean, vivid look.
  2. Create the red stripes by arranging rows of sliced strawberries flat across the length of the cake, keeping each row uniform in height and spacing. Continue until you reach the far edge.
  3. Fill the white stripes by piping extra frosting in rows between the strawberry rows, or place thin banana slices for the white bands. Pipe in straight lines for a crisp pattern, or align the banana slices edge-to-edge.
Chill and slice
  1. Refrigerate the decorated cake until ready to serve, about 1 hour, to set the buttercream and firm the fruit rows. Slice into squares right before serving for the cleanest cuts.

Notes

Pro tip: dry your berries well and keep the frosting spreadable—if it gets too stiff, mix in a splash more heavy cream (1 tbsp at a time). Refrigerate leftovers up to 3 days; the fruit topping softens over time. Freezing is not recommended because strawberries and bananas can weep and lose texture. For a gluten-free swap, use a 1:1 gluten-free white cake mix and follow its package bake directions for the same pan size.