Preheat oven to 350 degrees and grease a muffin tin.
In a small bowl, stir the milk and apple cider vinegar together to make dairy-free buttermilk and set aside to rest for 5 minutes.
1 cup almond milk, 1 teaspoon apple cider vinegar
In a medium bowl, whisk together the oat flour, cocoa powder, tapioca starch, and baking soda.
2 1/4 cups oat flour, 1/2 cup cocoa powder, 1 1/2 tablespoons tapioca starch, 1 tablespoon baking soda
In a large bowl, whisk together the apple sauce, coconut sugar, "buttermilk", and vanilla.
1 1/4 cups unsweetened apple sauce, 2/3 cup coconut sugar, 1 teaspoon vanilla
Add the dry ingredients to the wet ingredients and whisk together until combined.
Let the batter rest for 30 minutes to allow the oat flour to soak up some of the liquid.
Give the batter another quick stir and pour it into the muffin tin. Bake for 25-28 minutes until the tops of the cupcakes feel firm to the touch.
Let the cupcakes cool for 15 minutes in the pan before placing them on a cooling rack to completely finish cooling.
Scoop the frosting into a piping bag with the tip of your choice and frost the cupcakes.