- 1 (18.25 ounce) package yellow cake mix
- 1 cup water
- 3 large eggs
- 1/3 cup vegetable oil
- Filling:
- 1/2 cup white sugar
- 1 teaspoon cornstarch
- 1/3 cup water
- 2 cups fresh blueberries
- Icing:
- 1 (16 ounce) package confectioners' sugar
- 1 (8 ounce) package cream cheese, softened
- 1/4 teaspoon vanilla extract
- 1 (8 ounce) container frozen whipped topping, thawed
- Preheat oven to 350 degrees F (175 degrees C). Grease a 9×13-inch baking dish.
- Beat cake mix with 1 cup water, eggs, and vegetable oil until smooth; pour into the prepared baking dish.
- Bake in the preheated oven until a toothpick inserted into the center comes out clean, 23 to 28 minutes. Cool in the pans for 10 minutes before removing to cool completely on a wire rack. Slice cake in half horizontally to make 2 layers.
- Combine white sugar and cornstarch in a saucepan; gradually stir in 1/3 cup water. Add blueberries and bring to a simmer over medium heat. Simmer until thickened, stirring occasionally, about 1 minute. Allow blueberry mixture to cool.
- Beat confectioners' sugar and cream cheese in a large bowl until smooth. Stir in vanilla extract and fold in whipped topping.
- Place one layer of cake on a large platter; spread blueberry mixture over cake. Arrange remaining cake layer over blueberry filling. Spread cream cheese icing over entire cake.