Preheat oven to 350 degrees. Mix all the dry ingredients. Blend in the coffee, mayonnaise and vanilla. Grease and flour an 8-inch round cake pan. Pour in the batter and bake in preheated oven for 45 minutes. Test to see if it's done by inserting a knife in the middle. If it comes out clean, that means the cake is done. Remove from oven and cool on a wire rack. Slice and serve.