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Perfect Flag Sheet Cake Recipe with Easy Creamy Vanilla Frosting

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A moist and fluffy sheet cake with vibrant red, white, and blue layers, topped with a silky smooth vanilla buttercream frosting, perfect for patriotic celebrations and summer gatherings.

Ingredients

Scale
  • 2 ½ cups (312g) all-purpose flour, sifted
  • 2 ½ tsp baking powder
  • ½ tsp baking soda
  • ½ tsp salt
  • 1 cup (227g) unsalted butter, softened (room temperature)
  • 1 ¾ cups (350g) granulated sugar
  • 4 large eggs, room temperature
  • 1 tbsp pure vanilla extract
  • 1 cup (240ml) buttermilk, room temperature (or 1 cup milk + 1 tbsp lemon juice, let sit 5 mins)
  • 1 ½ cups (340g) unsalted butter, softened (for frosting)
  • 6 cups (720g) powdered sugar, sifted
  • 2 tsp pure vanilla extract (for frosting)
  • 4–6 tbsp (60–90ml) heavy cream or whole milk (for frosting)
  • Pinch of salt (for frosting)
  • Red and blue gel food coloring
  • Fresh blueberries (for decorating stars)

Instructions

  1. Preheat oven to 350°F (175°C). Grease and flour a 9×13-inch sheet cake pan or line with parchment paper.
  2. In a medium bowl, whisk together sifted flour, baking powder, baking soda, and salt.
  3. In a large bowl, beat softened butter and granulated sugar with an electric mixer on medium speed until pale and fluffy, about 3–4 minutes.
  4. Beat in eggs one at a time, fully incorporating each before adding the next. Mix in vanilla extract.
  5. With mixer on low, alternately add dry ingredients and buttermilk in three parts, starting and ending with dry ingredients. Mix just until combined.
  6. Divide batter into three portions: tint one third blue, one third red with gel food coloring, leave one third plain (white).
  7. Pour blue batter into bottom left corner of pan forming a rectangle. Add red batter in three stripes across remaining pan. Fill spaces between red stripes with white batter. Smooth gently.
  8. Bake for 35–40 minutes or until a toothpick inserted in center comes out clean. Let cool completely in pan on wire rack (about 1 hour).
  9. For frosting, beat softened butter on medium speed for 2 minutes until creamy. Gradually add powdered sugar, 1 cup at a time, mixing on low speed.
  10. Add vanilla extract, heavy cream, and salt. Beat on high speed for 3–5 minutes until light and fluffy. Adjust cream or sugar for desired consistency.
  11. Spread a thin crumb coat of frosting over cooled cake and chill for 15 minutes.
  12. Apply a final smooth layer of frosting. Use remaining blue frosting to pipe a small rectangle in top left corner and place fresh blueberries on top to mimic stars. Use red frosting for accents if desired.
  13. Chill cake for 30 minutes before serving to set frosting.

Notes

Use gel food coloring to prevent batter and frosting from becoming runny and to achieve vibrant colors. Room temperature ingredients ensure smooth mixing. If frosting is too soft, chill and re-whip. Brush cake lightly with simple syrup if dry. For gluten-free, substitute flour with 1:1 gluten-free blend. For dairy-free, use vegan butter and coconut or almond milk.

Nutrition

Keywords: flag cake, sheet cake, vanilla buttercream, patriotic dessert, Fourth of July cake, easy cake recipe, summer dessert

Find it online: https://islatable.com/perfect-flag-sheet-cake-recipe-with-easy-creamy-vanilla-frosting/