Preheat oven to 350 degrees.
Mix first 5 dry ingredients (flour, cocoa, sugar, baking soda, and salt) in a greased 8" square baking pan.
Make 3 depressions in dry ingredients - two small, one larger (we made a smiley face).
Pour vinegar in one of the smaller depressions.
Pour vanilla in the other small depression.
Pour vegetable oil in third larger depression
Pour water over all entire mixture.
Mix well until smooth.
Bake on middle rack of oven for about 35 minutes.
Check with toothpick to make sure it comes out clean.
Let cool before serving.