Preheat oven to 425ºF. Line a standard muffin tin with cupcake liners.
In a large bowl, whisk the flour, baking powder, baking soda, and salt together.
In a separate bowl, mix the oat milk, maple syrup, and vegetable oil together. Stir in the mashed banana. Using a rubber spatula, fold the wet ingredients into the dry ingredients until combined. Fill the liners ⅔ of the way up with batter.
Bake for 5 minutes, then lower the oven to 375ºF and continue baking for another 14-15 minutes. Allow muffins to cool in pan for 5 minutes before transferring to a wire cooling rack.
Notes
If you can't find oat milk, or can't have oats, feel free to use your favorite plant-based milk.
Make sure the oat milk you are using is made with gluten-free oats.