Heat oven to 350 degrees. Grease and lightly flour two 9-inch round cake pans; set aside.
In medium bowl, combine flour, cocoa, baking soda and baking powder; set aside. In large bowl, with electric mixer at high speed, beat eggs, sugar and vanilla for 3 minutes or until light and fluffy. Beat in mayonnaise at low speed until blended. Alternately beat in flour mixture with water, beginning and ending with flour mixture. Pour into prepared pans.
Bake 30 minutes.
Bake Read more here: http://www.kansascity.com/living/liv-columns-blogs/chow-town/article61643617.html#storylink=cpy