Buttercream Flag Cake (Simple 4th of July Party Dessert)
This buttercream flag cake starts with a doctored vanilla cake mix and bakes with a red and blue swirl inside. It’s topped with easy piped stars in red, white, and blue to form an American flag—no decorating skills needed. A fun and festive 4th of July dessert that looks impressive but is surprisingly simple to make.
Servings 12 to 18 slices
Calories 410kcal
Equipment
- measuring cups and spoons For accuracy.
- mixing bowls For dividing and coloring the frosting.
- Stand Mixer or hand mixer. To mix the batter and beat the frosting.
- piping bags and large star tip For decorating the flag design.
Ingredients
Cake:
- 1 box vanilla cake mix
- 1 cup (240 g) full-fat sour cream
- ½ cup (120 ml) whole milk
- ⅓ cup (75 g) butter melted
- 2 large eggs room temperature
- blue food coloring
- red food coloring
Buttercream Frosting:
- 1 cup (227 g) butter room temperature
- 1 cup (190 g) vegetable shortening
- 2 lbs (907 g) confectioners' sugar
- 1½ tbsps. (22 ml) water
- 1½ tsps (7 ml) vanilla extract
- red food coloring
- blue food coloring
- 1 tbsp red, white and blue sprinkles (optional)
Instructions
- Preheat oven to 350°F (175°C). Grease a 9x13-inch (23x33 cm) baking pan.
- In a large mixing bowl, combine the cake mix, sour cream, milk, melted butter, and eggs. Beat on high speed for 4 minutes until smooth.1 box vanilla cake mix, 1 cup (240 g) full-fat sour cream, ½ cup (120 ml) whole milk, ⅓ cup (75 g) butter, 2 large eggs
- Pour the batter into the prepared pan and spread it evenly.
- Add drops of blue food coloring across the top and swirl gently with the back of a spoon. Repeat with red food coloring, swirling without overmixing or you'll make a purple colored cake.blue food coloring, red food coloring
- Bake for 25–28 minutes, or until a toothpick inserted in the center comes out clean. Let the cake cool completely before frosting.
- While the cake cools, make the buttercream: beat the butter and shortening on medium-high until combined and fluffy.1 cup (227 g) butter , 1 cup (190 g) vegetable shortening
- Reduce mixer speed to low and gradually add the confectioners’ sugar. Once incorporated, add water and vanilla. Beat on high for 4–6 minutes until smooth and fluffy.2 lbs (907 g) confectioners' sugar, 1½ tbsps. (22 ml) water, 1½ tsps (7 ml) vanilla extract
- Divide frosting into three bowls. Tint one red, one blue, and leave one white. Transfer each to a piping bag fitted with a large star tip.red food coloring, blue food coloring
- Flip the cooled cake onto a tray or leave it in the pan.
- Pipe a blue rectangle in the top left corner using frosting stars—four rows, about 5 inches (13cm) long and 3 inches (7.5cm) tall.
- Pipe red and white stars in alternating stripes across the cake, starting with red. Add sprinkles if using.1 tbsp red, white and blue sprinkles
Notes
- Cake must be fully cooled before decorating or the buttercream will melt.
- Add water to the frosting a teaspoon at a time if it's too thick.
- You can frost the cake while it's in the pan or flip it onto a tray to use the flat bottom.
- Store leftovers in the refrigerator for up to 3 days.
- The unfrosted cake can be frozen (tightly wrapped) for up to 1 month.
Nutrition
Serving: 92g | Calories: 410kcal | Carbohydrates: 53g | Protein: 2g | Fat: 21g | Saturated Fat: 9g | Polyunsaturated Fat: 2g | Monounsaturated Fat: 5g | Cholesterol: 50mg | Sodium: 310mg | Potassium: 60mg | Sugar: 39g | Vitamin A: 430IU | Calcium: 60mg | Iron: 1mg