In a large bowl, bring together dry ingredients: flour, baking powder, baking soda, ground cinnamon, sugar, and salt. Mix well.
Add wet ingredients - vegetable oil, vanilla extract, eggs, pumpkin puree and mashed bananas. Stir to combine.
Line a 12-cup muffin tin with liners or grease muffin tin. Fill each cup with batter until it is 3/4 full. (See Note 1)
Bake for 25 minutes. Remove from oven. Insert toothpick into one of the muffins and if it comes out clean, muffins are done.
Let muffins cool in muffin tin for 3 minutes. Then remove them and let them cool on a cooling rack for 10-15 minutes.
Serve and enjoy!
Notes
Note 1: Batter typically makes 12-16 muffins. If there is leftover batter after filling the 12-cup muffin tin, I usually bake the rest on a second batch.