Easy Flag Cake Recipe

Cake

1. Preheat oven to 350°F and grease a 9" x 13" baking dish.
2. 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.
3. 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.
4. 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.
5. Bake the cake until a toothpick inserted in the middle comes out clean, about 30 - 35 minutes. Cool completely before frosting with buttercream.

Frosting

1. Beat the butter in a large mixing bowl or stand mixer until it is light and fluffy. Add salt and mix.
2. 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.
3. 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. 
4. Frost cake, making sure it's smooth. Reserve about 1 cup frosting for decorating.

Flag

1. 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.
2. Place buttercream in a piping bag with a star tip.
3. Alternate rows of sliced strawberries and piped buttercream stars across the cake to complete the flag.