Preheat the oven to 350 degrees Fahrenheit and spray three 6" cake pans with cooking spray.
In a small bowl, whisk together the sorghum flour, brown rice flour, starch, baking powder, cinnamon and salt.
In a stand mixer bowl with whisk attachment, add the pumpkin, soy milk, egg whites, vanilla sugar, oil and extracts. Whisk on medium/low speed.
Add the vinegar to the mixing stand mixer, then slowly add in the dry ingredients. When all is incorporated, scrape down the sides of the bowl. Whip batter on medium/high speed for 20-30 seconds.
Pour batter into the three prepared pans and bake for 28-33 minutes, or until the surface of the cakes spring back when tapped.