Preheat oven to 350° F. Grease and flour a 9x5-inch loaf pan.
In a medium mixing bowl, whisk together the gluten free flour blend, baking soda, baking powder, salt, pumpkin pie spice, and cinnamon until combined.
In a large mixing bowl, whisk together the oil, sugars, eggs, and vanilla until completely combined.
Add the mashed bananas and pumpkin puree to the egg mixture and stir until combined.
Using a wooden spoon, stir the dry ingredients into the wet ingredients until combined.
Transfer the batter to the prepared pan and bake for 50 - 60 minutes or until a wooden pick inserted into the middle comes out clean.
Cool the bread in the pan for 15 minutes before removing to a wire rack to cool completely.
Generously grease and flour the loaf pan. Doing this will prevent the bread from sticking to the pan.
Make sure to use pumpkin puree, not pumpkin pie filling. Pumpkin pie filling has added sugar in it and will make the bread overly sweet.
Mix the dry ingredients and the wet ingredients well before stirring them together. Once you add the two together, over mixing the batter can lead to bread that is tough. Even though gluten free flour doesn’t contain gluten, the xanthan gum can add toughness if overmixed.
Check to make sure the bread is done before removing from the oven. Using a wooden pick or cake tester, insert it into the center of the bread. If the pick comes out clean the bread is done. If not, continue baking for a few more minutes and check again.