Adapted from Moosewood Chocolate Cake* (double the recipe if you love cake)
Preheat the oven to 375°.
Sift the flour, cocoa, baking soda, salt and sugar into a big bowl.
In a separate bowl,mix the oil, water or coffee and vanilla. Add the liquid ingredients to the dry ingredients and mix the batter with electric mixer.
When the batter is smooth, add the vinegar and stir only until the vinegar is evenly distributed into the batter.
Transfer the batter into an 8 inch square or round pan... or two if you doubled the recipe.
Bake for 25-30 minutes (do the toothpick test). Cool completely.
* I decreased the amount of vinegar.