The Ultimate Chocolate Cake

2 cups unsifted flour
2/3 cup cocoa
1 1/4 teaspoon baking soda
1/4 teaspoon baking powder
1 2/3 cups sugar
4 eggs
1 teaspoon vanilla
1 cup best foods mayonnaise
1 1/3 cups water

Grease and flour bottoms of 2 9" layer cake pans. Mix first 4 ingredients; set aside. In large bowl with mixer at high speed, beat next 3 ingredients 3 minutes or until light and fluffy. At low speed beat in mayonnaise. Add flour mixture in 4 additions alternatively with water. Beginning and ending with flour. Pour into pans and bake in 350 degree oven for 30 to 35 minutes or until cake tester inserted in center comes out clean. Cool in pans for 10 minutes. Remove and cool on racks.