Preheat oven to 350 degrees F and grease a 9 x 13 inch baking pan, set aside.
In a large bowl, whisk together the pumpkin puree, mashed bananas, sugar, brown sugar, melted butter and eggs until combined. It's ok if it looks slightly chunky because of the bananas.
Stir in the flour, baking soda, baking powder, salt, cinnamon and pumpkin pie spice. Be sure to us a rubber spatula to scrape down the sides of the bowl. Pour the batter into the prepared baking pan and evenly spread the batter with a spoon or spatula.
Bake for 25-30 minutes or until an inserted toothpick comes out clean and the top of the bread feels firm. Let the bread cool for 15 minutes before slicing into bars. Dust with powdered sugar and enjoy!