Whisk together your flour, baking powder, salt and cinnamon in a medium sized bowl and set it aside.
In another medium sized bowl, beat your bananas, then add in your sugars and egg.
Mix in your milk, scraping down the sides of the bowl as needed, then your peanut butter, then your oil, then your vanilla, scraping down the bowl after each is incorporated.
Grease and/or line 20 muffin cups and scoop batter into each one, filling just below the top of each muffin cup.
Sprinkle with a generous amount of sugar, then bake for 20-25 minutes, until golden.
Allow the muffins to cool for 10 minutes or so before removing from the tins.
Recipe by at https://laurasglutenfreekitchen.com/2018/03/gluten-free-peanut-butter-banana-muffins/