Preheat the oven to 350 degrees Fahrenheit and spray two 6"x3" cake pans with cooking spray.

In a stand mixer bowl with whisk attachment, add the applesauce, almond milk, egg whites, vanilla sugar, oil, vanilla extract, stevia extract and almond flavor. Mix on low speed.

In a small bowl, whisk together the brown rice flour, oat flour, corn starch, baking powder, baking soda and salt.

Add the vinegar to the stand mixer bowl, still on low speed.

Slowly add the dry ingredients and well it is all incorporated, beat on medium/high speed for ~20 seconds.

Pour the batter evenly between the two pans. Bake for ~53 minutes, or until the edges are golden brown and surface is firm when tapped.

In a microwave-safe bowl, add ¼ cup of yogurt and the coconut oil and microwave at 10-second intervals, stirring between each one, until the oil is softened/melted, but NOT hot.

Scoop mixture into a stand mixer bowl with whisk attachment, and add the vanilla paste and butter extract.

Add the erythritol and beat on high speed for a few minutes, or until fluffy and light (if you need more yogurt, add it 1 tablespoon at a time).  Frost the cake.  Slice and serve!