"This is our go-to cake recipe now. After years of making 'depression cake' for our egg- and dairy-allergic son, we finally discovered that xanthan gum is the necessary ingredient for combating crumbly cake! This can easily be a vegan cake, or a not-necessarily-vegan cake, you throw together with stuff in your pantry! Cool completely, frost as desired, and enjoy!"
Preheat oven to 350 degrees F (175 degrees C). Spray a 9x13-inch baking dish with cooking spray.
Whisk flour, cocoa powder, xanthan gum, baking soda, and salt together in a bowl. Add water, sugar, vegetable oil, vinegar, and vanilla extract to dry ingredients; mix until batter is just moistened and pour into the prepared baking dish.
Bake in the preheated oven until a toothpick inserted in the center of the cake comes out clean, about 40 minutes.