Preheat oven @ 350 degrees
Dissolve 2 tsp baking soda into 1 c boiling water
Mix 1 c mayonnaise, 1 cup sugar, 1tsp vanilla until blended
Sift 2 cups flour with 1/2 cup cocoa & a pinch of salt
Beat all together
Grease 1 round or square cake pan & bake for 25-30 min
Frost with cream cheese frosting
Double recipe for a 9 x 13 cake pan