Preheat the oven to 350°F (175°C). Coat four mini loaf pans or two standard loaf pans with nonstick cooking spray, then set them aside.
Place the ripe bananas in a large mixing bowl. Mash them until mostly creamy while retaining a small amount of texture.
Add the granulated sugar, packed brown sugar, vegetable oil, eggs, pumpkin purée, vanilla extract, and pumpkin pie spice to the mashed bananas. Stir thoroughly until the ingredients are evenly combined. A slightly lumpy consistency is expected because of the bananas.
In a separate bowl, combine the gluten-free flour blend, cinnamon, baking powder, baking soda, ginger, and nutmeg. Stir well to distribute the leavening agents and spices uniformly.
Add approximately half of the dry mixture to the wet ingredients. Blend gently with a large spoon or a mixer set to low speed until just incorporated.
Add the remaining dry ingredients and continue mixing only until no visible pockets of flour remain. Avoid excessive mixing to preserve the bread’s tender texture.
Distribute the batter evenly among the prepared loaf pans, filling each pan approximately three-quarters full. Keep the portions as equal as possible to encourage consistent baking.
Transfer the pans to the preheated oven. Bake for 40–45 minutes, or until a toothpick inserted into the center of a loaf emerges clean. Begin checking mini loaves at the 30-minute mark to prevent overbaking.
Remove the finished loaves from the oven and allow them to rest in their pans for approximately 10 minutes.
Carefully release the loaves from the pans and transfer them to a wire cooling rack. Let them cool completely before slicing and serving.