Sift and blend flour, sugar, cocoa, baking soda and salt.
2 Add mayonnaise, water and vanilla. Stir until mixed well.
3 Grease a 9x13 pan and pour batter in evenly.
4 Bake at 350 degrees for 20 minutes or until a toothpick comes out clean.
For the Frosting
5 Combine cream cheese and butter, beating until smooth.
6 Add sugar and vanilla, beat until light and fluffy.