Preheat oven to 400 °F (204 °C). Line a standard 12-cup muffin pan with muffin liners and set aside. This recipe makes 16 so you can either line a second muffin pan with 4 more or use the same muffin pan after the first batch is done baking.
In a large bowl, whisk together dry ingredients (flour, baking powder, baking soda, cinnamon/pumpkin pie spice, sugar, and salt. Set aside.
1 1/2 cup all purpose flour, 1 teaspoon baking powder, 1 teaspoon baking soda, 2 teaspoons ground cinnamon or pumpkin pie spice, 1 cup granulated sugar, 1/2 teaspoon salt
In another bowl, whisk together liquids (mashed bananas, oil, vanilla bean paste, eggs, and pumpkin puree) until combined.
3 ripened bananas, 1/3 cup neutral oil such as avocado or vegetable oil, 1/2 teaspoon vanilla bean paste, 2 large eggs, 3/4 cup pumpkin puree
Make a well in the center of the dry ingredients then pour the liquid mixture into the well. Using a spatula, gently fold the mixture together until all incorporated and no flour or clumps (aside from mashed banana chunks) remain.
Using a large cookie scoop, scoop batter into lined muffin pan, filling about 2/3 full.
Bake at 400 °F (204 °C) for 5 minutes then reduce oven temperature to 350 °F (177 °C) and bake for another 12 minutes.
Insert a toothpick into the center of the muffin and if it comes out clean, remove from oven and allow to cool for 10 minutes then carefully remove muffins and place them on a wire cooling rack to cool completely.
Notes
If you need to bake a second batch, turn the oven back to 400 °F and follow the directions again from step 5.