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American Flag Cake

American flag cake made as a full patriotic sheet cake: white buttercream frosting topped with a blueberry canton, strawberry red stripes, and banana or extra frosting white stripes. This 4th of July cake bakes in a sheet-pan style layout for easy slicing into clean squares with vivid rows.
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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
Ingredients Equipment Method Notes

Ingredients
  

White cake
  • 2 box white cake mix Use cake mix directions for eggs, water, and oil/butter.
Buttercream frosting
  • 2 cup unsalted butter Softened.
  • 6 cup powdered sugar
  • 2 tsp vanilla extract
  • 4 tbsp heavy cream Add 4–6 tbsp until spreadable.
Flag fruit topping
  • 2 cup fresh blueberries Reserve for the canton.
  • 2 lb fresh strawberries Hulled and sliced lengthwise for stripes.
  • 1 banana slices Optional: use instead of extra white frosting for the white stripes.

Equipment

  • 1 sheet pan

Method
 

Bake the sheet cake
  1. Bake both boxes of white cake mix in a large 12x18 sheet pan (or two 9x13 pans joined) according to package directions, until a toothpick comes out clean. Cool completely before frosting.
Make white buttercream
  1. Beat softened unsalted butter until fluffy, then gradually add powdered sugar and mix until combined. Beat in vanilla extract and 4–6 tablespoons heavy cream until smooth and spreadable, about 2–3 minutes.
Frost the cake
  1. Frost the entire top of the cooled sheet cake with a thick, even layer of buttercream so the fruit toppings sit flat. Smooth the surface gently with an offset spatula or the back of a spoon for clean stripe lines.
Decorate the American flag
  1. In the upper left corner, arrange fresh blueberries into a dense rectangle to form the canton. Pack them close together so the grid looks filled from edge to edge.
Add red strawberry stripes
  1. Create red stripes by arranging sliced fresh strawberries flat across the length of the cake in uniform rows. Keep each row parallel so the stripes look straight from an overhead view.
Add white stripes
  1. Fill the white stripes by piping extra frosting in rows between the strawberry rows, or place thin banana slices for the white bands. Use even pressure to keep the white stripes the same thickness across the cake.
Chill and serve
  1. Refrigerate the decorated cake until the frosting is set, then slice into squares and serve. Keep leftovers refrigerated for up to 3 days.

Notes

Pro tip: for the cleanest red stripe look, slice strawberries lengthwise to a consistent thickness and keep the rows tight and parallel. Refrigerate the finished cake for up to 3 days; freezing is not recommended because fruit toppings can release moisture. For a lighter option, use reduced-fat butter and swap half the powdered sugar for cornstarch-free confectioners sugar alternatives, then adjust cream to keep the frosting spreadable.