Preheat oven to 350 degrees F (176 C) and lightly grease two standard 8-inch round cake pans, one 9x13-inch, or three 6-inch round pans* (with vegan butter or coconut oil) and dust with gluten-free flour. Shake out excess and set aside.
In a liquid measuring cup, measure out dairy-free milk and add vinegar. Let set a few minutes. Then add applesauce and vanilla. Whisk/stir to combine.
Add dry ingredients to a large mixing bowl and whisk to combine. Then add wet ingredients to the dry ingredients and mix until well incorporated and no large lumps remain. The batter should be thick but pourable. Add more almond flour if too wet or dairy-free milk if too thick.
Divide batter evenly between prepared cake pans and bake on a center rack for 35-40 minutes or until a toothpick inserted into the center comes out clean and the edges and surface appear golden brown.
Let cool 15 minutes in the cake pans. To remove from pans, run a dull knife around the edge of the pans to loosen the cakes. Then place a plate or cooling rack on top and quickly invert. Let cool completely (preferably overnight or at least 6 hours on a wire rack) before frosting.
Store cake covered at room temperature for 2-3 days or in the refrigerator for 3-4 days. Freeze up to 1 month.
FROSTING*: Add softened butter to a large mixing bowl and beat for 1 minute. Then add vanilla and mix once more. Gradually add sifted powdered sugar 1 cup at a time and beat until a thick, spreadable frosting is formed. I found about 3 1/2 cups to be the appropriate amount per 1 full cake recipe.
If too thick, the frosting will be too hard to spread (add 1/2 tsp almond milk at a time if too thick). If too thin, the frosting will slide off the cake. If too thin, continue adding powdered sugar until you get the right texture.
Use immediately or cover and store in the refrigerator up to 5 days. Let come to room temperature before frosting.
*If altering batch size, please note that the number of pans and frosting instructions are based on how the original recipe is written. Adjust accordingly. *To reduce sugar, each 1/4 cup of sugar be swapped with 1 packet (1/2 tsp) of powdered stevia. Or you could try subbing a mix of maple syrup and coconut sugar, but I haven’t tested it this way and can’t guarantee results. *Nutrition information is a rough estimate calculated with the salt and without frosting. *Prep time does not include cooling the cake. *Recipe inspiration from The Vegan 8.