Preheat the oven to 350 degrees F. Line a muffin tin with cupcake liners.
In a medium bowl, whisk together the dairy-free milk and apple cider vinegar.
In a large bowl or stand mixer, combine the almond flour, brown rice flour, coconut sugar, baking powder, baking soda, and sea salt. Stir until blended.
To the bowl with the milk and apple cider vinegar mixture, add the beaten egg, mashed banana, maple syrup, and vanilla extract. Whisk until creamy.
Pour the wet ingredients into the bowl with the flour mixture. Beat until a batter is formed.
Evenly transfer the batter to the cupcake-lined muffin tin, filling each one about 3/4 of the way to the top. Bake for 20 to 22 minutes, or until a toothpick inserted comes out clean. Allow the cupcakes to completely cool (at least 1 hour) before frosting.
To make the frosting, combine the grass-fed butter, coconut oil, and cream cheese in a large bowl. Using a hand beater, stand mixer, or hand blender with the whisk tool, beat until fluffy, about 30 seconds. Scrape down the sides of the bowl. You can also whisk by hand if needed. Add the powdered monk fruit and vanilla extract and beat again. Give the frosting a good stir with your spatula. Frost the cupcakes immediately, or put the frosting in the refrigerator for 10 minutes for a firmer texture.