Preheat oven to 350 degrees F. Spray an 8-inch square pan with nonstick cooking spray.
Mix first 5 dry ingredients in the prepared pan (flour, cocoa powder, sugar, baking soda and salt.)
Make 3 depressions in the dry ingredients – two small, one larger.

Pour vinegar in one of the smaller depressions. Pour the vanilla extract in the other smaller depression and the vegetable oil in the third larger depression.
Pour water over all. Mix well until smooth.
Bake on the middle rack of the oven for 35 minutes. Check with toothpick to make sure it comes out clean. Note: Oven baking times may vary, be sure to check your cake to make sure you do not over bake.
Cool completely before frosting (if using). You can also just sprinkle with a dusting of powdered sugar.

Top cooled cake with powdered sugar or favorite frosting:
Top with your favorite frosting or a dusting of powdered sugar.
Store frosted cake in the refrigerator.