Prep - Start by preheating the oven to 350 degrees F and lining a muffin tin with paper liners. You'll likely need to bake in two batches.
Mix Dry Ingredients - In a large bowl, whisk together the dry ingredients (flour, baking powder, baking soda, cinnamon, white sugar, brown sugar, and salt) until combined. Use a whisk helps remove any lumps.
Mix Wet Ingredients - In a medium bowl, mix together the wet ingredients (oil, vanilla, eggs, pumpkin, mashed bananas) until combined.
Mix Batter - Add the wet ingredients to the dry and fold to combine. Don't over mix.
Fill Muffin Tin - Fill the muffin tin with the batter. Fill each cup about 3/4 full.
Bake - Bake the muffins for 20-23 minutes until they are set and a toothpick inserted in the center comes out clean or with a few moist crumbs. Repeat with remaining batter.
Enjoy - Allow them to cool in the tin for a few minutes before removing to a cooling rack.
Leftovers - Leftover muffins can be stored in an airtight container at room temperature for up to 4 days.
Freezing - Muffins freeze well to enjoy for months! I like to flash freeze on a baking sheet first before transferring to an airtight freezear bag. Freeze for up to 3 months. For best results, thaw at room temperature then enjoy room temperature or warm for a few seconds in the microwave.
Use Toothpick to test Doneness - Instead of solely relying on time, I recommend using a toothpick inserted into the center of a muffin to test for doneness. There should be no wet batter but just some moist crumbs (or fully clean).
Super Ripe Bananas - The riper the bananas, the sweeter they will be! You want bananas that are super brown and soft.