Super-Moist Chocolate-Mayo Cake

1 (18.25-ounce) package chocolate cake mix
1 cup mayonnaise
1 cup water
3 eggs
1 teaspoon cinnamon (optional)

Preheat oven to 350 degrees. Grease and flour a 9 x 13 x 2-inch pan. Combine cake mix, mayonnaise, water, eggs and cinnamon. Pour into prepared pan. Bake as directed on cake box.
Makes 8 servings