Preheat oven to 350°. Lightly spray 8 x 8 inch square pan with cooking spray.
In a small bowl combine flour, xanthan gum, salt, baking powder, and cocoa. Mix and set aside.
In a large bowl, whisk oil and eggs together until combined. Add vanilla and sugar. Slowly mix in flour mixture and water. Once all flour is combined, spread evenly into pan. Allow the batter to rest for at least 5 minutes in the pan (this allows the flour and binders to hydrate fully.)
Bake on center rack for 30-35 minutes or until toothpick comes out with just a few crumbs.
Cool completely and serve.
For more chocolate flavor add ½ cup chocolate chips. For crunch, add ½ cup chopped pecans or walnuts.