Preheat your oven to 300°F (150°C), then coat a 9x5-inch loaf pan with nonstick spray. Line the bottom and up each end of the pan with a strip of parchment paper, so the ends hang over the pan slightly. Spray again with the nonstick spray, then set aside.

In a large bowl, mix together the granulated sugar and vegetable oil. Add in the eggs and vanilla extract and mix until smooth.

Stir in the mashed bananas, pumpkin, baking soda, kosher salt, and pumpkin pie spice until all the ingredients are combined.

Add the flour, and fold until just combined. Be careful not to overmix.

Pour the pumpkin banana bread batter into the prepared pan.

In a medium bowl, add all of the ingredients for the crumb topping (cold butter, dark brown sugar, flour, and pumpkin pie spice). Use a pastry cutter, fork, or your hands to mix until it forms coarse crumbs.

Sprinkle the crumb topping evenly over the pumpkin banana bread batter in the pan.

Bake for 65-85 minutes, or until a toothpick inserted into the center of the bread comes out clean. If the crumb topping begins to brown too much before the bread is fully cooked, loosely cover with foil.

Allow the bread to cool in the pan for 20 minutes. Then, using the parchment paper as a handle, carefully transfer it to a wire rack to cool completely.

Serve warm or at room temperature. Store any leftovers tightly covered at room temperature for up to 3 days, or refrigerate for longer storage.