The Best Funfetti Butter Cake

Name: Funfetti Butter Cake
Yield: 12
Ingredients: 1 (8-ounce) brick cream cheese, room temperature; 8 tablespoons butter, melted; 2 large eggs; 1 tablespoon clear vanilla extract; 3 1/2 cups powdered sugar; 1/4 cup rainbow sprinkles; 1 box yellow cake mix; 1 large egg; 8 tablespoons butter, melted; 1 teaspoon clear vanilla extract; 1/4 cup rainbow sprinkles