Combine dry ingredients in a large mixing bowl, tossing lightly with a spoon to mix. Combine the mayonnaise, coffee, and vanilla in a smaller bowl; add to the dry ingredients, beating with the mixer on medium for three minutes.
Generously grease a baking pan, then dust with cocoa. Bake at 180ºC . For a layer cake, bake 20 minutes; for a sheet cake, bake 25 minutes; for a bundt cake, bake 45 minutes.
Note: If it falls, don't throw it out, it masquerades as wonderful brownies!