Preheat the oven to 350 degrees F and grease two 8-inch cake pans. I also line them with parchment rounds for easy removal of the cakes later.
Measure 1 cup soy milk in a glass measuring cup and add vinegar. Stir slightly and set aside.
In a large bowl, whisk together the gluten free flour, xanthan gum, sugar, cocoa powder, baking powder, baking soda and salt.
To the bowl with the dry ingredients, add the oil, applesauce, vanilla and milk/vinegar mixture. Mix on medium speed with a hand mixer (or stand mixer with the whisk attachment) until well combined.
Lower the speed and carefully pour in the boiling water, continuing to mix into the cake batter until combined. The batter will be quite runny at this point.
Divide the batter evenly between your cake pans. Bake for 30-35 minutes, or until a toothpick inserted in the center comes out clean. After 10 minutes of cooling in the pan, carefully remove the cakes from the pans and let cool completely before frosting.
Only once the cake is completely cooled, frost with chocolate frosting using an icing spatula or just a butter knife and enjoy! It’s fine to store the cake at room temperature for 1-2 days, or you can refrigerate it for 3-4 days. Make sure to cover any cut parts so it doesn't dry out.