This fun flag cake recipe not only looks like an American flag on the outside, the inside is also swirled full of red, white, and blue color! It’s the perfect patriotic cake for any red, white, and blue occasion!
Preheat oven to 350°F and grease a 9" x 13" baking dish.
Combine cake mix, water, egg whites, oil, sour cream, and vanilla in a large mixing bowl or stand mixer. Mix on low speed until ingredients are combined, then beat on medium speed for 2 minutes, scraping the sides of the bowl as needed.
1 box white cake mix, 1/4 cup water, 4 egg whites, 1/2 cup vegetable oil, 1 cup sour cream, 1 tsp clear vanilla extract
Pour 2 cups of the cake batter into the prepared baking dish, then divide the remaining cake batter into two separate bowls. There will be about 3/4 cup batter in each bowl. Add a different color food coloring to each bowl, mix until color is consistent. Use more or less food coloring to get desired color.
red and blue food coloring
Use a spoon to drop dollops of each of the colored batters randomly over the white cake batter in the pan then use a butter knife and run it back and forth through the batter to swirl the colored batter into the white batter. Make sure you don't overdo it or you'll end up with one color instead of swirls.
Bake the cake until a toothpick inserted in the middle comes out clean, about 30 - 35 minutes. Cool completely before frosting with buttercream.
Frosting
Beat the butter in a large mixing bowl or stand mixer until it is light and fluffy. Add salt and mix.
1/2 cup butter, 1/4 tsp salt
Slowly add powdered sugar a little at a time, mixing on low speed until all powdered sugar is added and mixed well with the butter. Scrape the sides of the bowl to make sure the butter gets mixed in well.
2 cups powdered sugar
Next, add the vanilla and two tablespoons of frosting. Beat for one minute and check consistency. If frosting is too thick, add a bit more cream and continue mixing until frosting is a good consistency for spreading.
1 1/2 tsp vanilla extract, 2-4 TBS heavy cream
Frost cake, making sure it's smooth. Reserve about 1 cup frosting for decorating.
Flag
After cake is frosted with buttercream, place 5 rows of 6 blueberries (or enough for the size "stars" you want) in the upper left corner of cake.
blueberries
Place buttercream in a piping bag with a star tip.
Alternate rows of sliced strawberries and piped buttercream stars across the cake to complete the flag.
strawberries
Notes
Ingredient Notes:
Clear vanilla – it’s important to use clear vanilla in the batter so that the dark color of regular vanilla doesn’t impact the coloring of the cake. You can get clear vanilla at Walmart, most grocery stores, and on Amazon here.
Eggs – I recommend using four egg whites but if you don’t have four eggs, you can also use three whole eggs. You will have a slight yellow tint to the cake but it’ll taste fine.
Butter – it doesn’t really matter if you use salted or unsalted for the frosting but if you do use salted, I recommend leaving out the added salt. You do want to make sure that the butter is nice and soft before you make this frosting – I like to leave it out overnight or for at least an hour.
Heavy cream - if you don't have heavy cream, you can substitute milk but you'll likely only need the two tablespoons since milk is thinner than cream.
Tips: Store cake in the fridge covered for up to four days. Cake can be served either chilled or at room temperature but the frosting with the heavy cream should be refrigerated.Switch up the colors and toppings and make this cake work for a different holiday as well!Don’t overdo the food coloring. Food coloring can give have a really strong taste if overused and you really only need a few drops to turn this white cake mix colorful!