Preheat the oven to 425°F.

Prepare a muffin tin by lining it with muffin liners or lightly greasing the cups.

Mash the ripe bananas (the more ripe the better!) in a large mixing bowl.

Add the pumpkin puree, granulated sugar, egg, vanilla extract, and vegetable oil; stir until well combined.

In a separate bowl, add the dry ingredients: all-purpose flour, baking powder, baking soda, baking powder, ground cinnamon, ground ginger, allspice, and salt.

Gently fold the dry ingredients into the wet ones, being careful not to overmix the batter.

Fill the prepared muffin cups about three-fourths full with the batter. The batter will be enough to fill 12 muffin cups.

Prepare the crumb topping by adding brown sugar, flour, and cinnamon together in a small bowl. Use a fork or pastry cutter to cut the butter into the flour mixture.

Break down the butter into small bits to create the crumb topping. Sprinkle the topping evenly over the muffin batter lightly pressing it into the top of the batter.

Place the muffin tin into the oven preheated to 425ºF and bake for 5 minutes.

Once the 5 minutes are up, without opening the oven, reduce the heat to 350ºF and bake for an additional 13 to 15 minutes.

Check the center of a muffin with a toothpick to make sure it comes out clean.

Allow the muffins to cool in the muffin tin for about 5 to 10 minutes.

Transfer your pumpkin banana muffins to a wire rack to cool completely.

Store in an airtight container.