Preparation Steps

• Preheat oven to 350°F and grease a 9x13 inch baking dish.
• In a large mixing bowl, beat cake mix, water, egg whites, oil, sour cream, and vanilla extract with an electric mixer on low speed for 30 seconds, then medium speed for 2 minutes, scraping the bowl edges occasionally.
• Pour 2 cups of the batter into the prepared pan.
• Divide the remaining batter into three medium bowls. Add a few drops of blue, pink, and yellow food coloring to each bowl and stir until the desired color is reached.
• Drop spoonfuls of each colored batter randomly over the white batter. Use a butter knife to gently swirl the colors together to create a tie-dye effect.
• Bake for 30 to 35 minutes or until a toothpick inserted into the center comes out clean. Cool completely before frosting.
• For frosting, whip the butter with an electric mixer for 1 to 2 minutes until fluffy and lighter in color.
• Add powdered sugar and salt to the butter and beat on low to medium speed for about 1 minute until combined.
• Add vanilla extract and 2 tablespoons of heavy cream; beat for 1 minute. If desired, add food coloring to the frosting. Adjust consistency with more cream as needed and whip until light and fluffy.
• Spread frosting evenly over cooled cake and decorate with sprinkles for a festive finish.