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American Flag Cake

American flag cake made as a patriotic sheet cake with a thick, even white frosting layer and a crisp blueberry canton plus strawberry red stripes. This 4th of July cake uses layered fruit rows over white buttercream for a clean, vivid red-white-blue finish.
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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: 480
Ingredients Equipment Method Notes

Ingredients
  

White cake
  • 2 boxes white cake mix Use the amount of water, eggs, and oil listed on the box for two boxes total.
  • eggs Use the quantity specified on the cake-mix boxes.
  • water Use the quantity specified on the cake-mix boxes.
  • vegetable oil Use the quantity specified on the cake-mix boxes.
Frosting
  • 2 cups unsalted butter Softened.
  • 6 cups powdered sugar
  • 2 tsp vanilla extract
  • 5 tbsp heavy cream Add 4–6 tbsp until spreadable.
Decoration
  • 2 cups fresh blueberries Keep dry for a neat canton.
  • 2 lb fresh strawberries Hulled and sliced lengthwise.
  • 1 cup banana slices Optional for white stripes, or use extra white frosting if preferred.
  • 1 cup extra white frosting Optional substitute for banana slices for the white stripes.

Equipment

  • 1 sheet pan

Method
 

Bake the sheet cakes
  1. Heat and bake both white cake mixes in a large 12x18 sheet pan (or two 9x13 pans joined together) according to package directions, until a toothpick comes out clean and the tops spring back at 325°F to 350°F. Let the cakes cool completely in the pans, then remove for frosting.
Make the white buttercream frosting
  1. Beat the softened unsalted butter until fluffy, about 2–4 minutes. Gradually add powdered sugar, then mix in vanilla and 1 tbsp heavy cream at a time until the frosting is smooth and spreadable, about 1–3 minutes, adding up to 4–6 tbsp total.
Frost the cake
  1. Spread a thick, even layer of buttercream across the entire cooled sheet cake top so it’s fully covered with an opaque white surface. Use an offset spatula to keep the finish level.
Arrange the American flag fruit design
  1. In the upper left corner, arrange the fresh blueberries into a dense rectangle to form the blueberry canton. Press them lightly so the shapes look tightly packed.
  2. Create the red stripes by arranging sliced strawberries flat across the length of the cake in long, uniform rows. Keep the spacing consistent so the stripes read clearly from overhead.
  3. Fill the white stripes by piping extra white frosting in rows between the strawberry rows, OR lay thin banana slices in the gaps for white stripes. Add enough to create visible, raised white lines between the red rows.
Chill and serve
  1. Refrigerate the decorated flag cake until the frosting is set, 30–60 minutes, then slice into squares to serve. Keep leftovers refrigerated in an airtight container.

Notes

Pro tip: dry the strawberries before slicing so the red rows don’t bleed juice into the white frosting. Refrigerate leftovers up to 4 days (best texture within 2 days); freezing is not recommended due to fruit texture. For a simple swap, use gluten-free white cake mix if you want it to be gluten-free while keeping the same decorating method.