Blueberry Crumb Cake comes together quickly with a yellow cake mix and is bursting with fresh blueberries! The crumbs on top and in the middle of the cake add the perfect texture to this simple but delicious cake.
Preheat the oven to 350°F. Grease a 13x9-inch cake pan. Set aside.
Place 2 cups of the cake mix in a bowl. Add the water and egg; mix on low speed with an electric mixer, then beat on medium speed for 2 minutes or until the batter is smooth and creamy.
Measure out 1 cup of the batter and set aside. Spread the remaining batter into the prepared pan; it will be a very thin layer. Set aside.
In a separate bowl, combine the remaining cake mix with the cinnamon. Stir in the vanilla and melted butter with a fork to form large crumbs.
Sprinkle half of the crumb mixture over the batter in the pan, breaking up large clumps of the crumbs as necessary. Spoon the remaining batter over the top, spreading to mostly cover the crumbs.
Sprinkle the blueberries over the batter, then top with the remaining crumbs, once again breaking up any large clumps as necessary.
Bake for 35 minutes, or until golden and a toothpick inserted into the center comes out clean.
Notes
If you would like to use frozen blueberries, do not thaw them first.