Mix flour, baking soda, baking powder, cocoa, and sugar
into a large bowl. Stir in mayonnaise. Gradually add water
and vanilla and blend until smooth. Pour batter into
prepared pans.
Bake at 350 degrees F (175 degrees C) for 30 minutes.
Cool, remove from pans, and frost with your favorite frosting. This is the perfect cake to use a fruit jam in the center and sprinkle with sifted powdered sugar.