Preheat your oven to 425F.
Grease a muffin pan with coconut oil, or use cupcake liners.
Mix flour, baking powder, baking soda, oats, and cinnamon in a medium bowl.
In a large bowl, whisk together the melted butter and sugars until well combined.
To the sugar/butter mixture, add the eggs, mashed banana, and vanilla, whisking until combined.
Combine the dry and wet ingredients and stir until just combined (no longer).
Gently fold your blueberries into the batter (drain if frozen).
Divide the batter between the muffin tin holes (keeping every other cup empty to add airflow) and fill them all the way to the top.
Bake for 5 minutes at 425F then, without opening the oven, drop the temp to 350F and bake for another 12-15 minutes, or until a toothpick inserted in the center comes out clean.
Allow the muffins to cool for 3 minutes in the muffin pan, then transfer them to a wire rack to continue cooling.