PREHEAT oven to 350º oven. Grease & flour two 9-inch cake pans.
CREAM sugar & margarine til fluffy.
BEAT in eggs, 1 at a time.
COMBINE flour, cocoa, baking soda & salt. Add alternately with mayonnaise while beating. Add vanilla & blend well.
POUR into prepared pans. Bake at 350º for approximately 35 minutes.