Preheat oven to 350°. Grease and lightly flour two 9-inch round cake pans*; set aside.
Beat cake mix, Hellmanns® or Best Foods® Real Mayonnaise, water, eggs and cinnamon 30 seconds in large bowl with electric mixer on low speed. Beat on medium speed, scraping sides occasionally, 2 minutes. Pour batter into prepared pans.
Bake 30 minutes or until toothpick inserted in centers comes out clean. Cool 10 minutes on wire rack; remove from pans and cool completely. Sprinkle, if desired, with confectioners sugar or fill and frost.
*Or, prepare cake mix as above in 13 x 9-inch baking pan and bake 40 minutes or until toothpick inserted in center comes out clean.
VARIATIONS: For A PECAN COCONUT TOPPED CAKE...combine 1 cup flaked coconut, 2/3 cup firmly packed brown sugar and 1/2 cup chopped pecans, then sprinkle over cake batter in 13 x 9-inch baking pan. Bake 1 hour or until toothpick inserted in center comes out clean.
For A BLACK FOREST CHOCOLATE CAKE...do not flour baking pan. Evenly spread 2 cans (21 oz. ea.) cherry pie filling over bottom of 13 x 9-inch baking pan, top with prepared cake batter and bake 1 hour or until toothpick inserted in center comes out clean. Cool completely, then turn upside down onto serving platter.
For A DECADENT CHOCOLATE LAVA...combine 2 packages (3.4 oz. ea.) instant pudding, 2 cups water, 2 cups milk and 1/3 cup sugar until blended, then pour over cake batter in 13 x 9-inch baking pan. Bake 1 hour or until toothpick inserted along edge comes out clean and serve warm.
For A YELLOW MAYONNAISE CAKE...substitute 1 box (18 oz.) yellow cake mix for chocolate cake mix.