Preheat the oven to 350°F. Line one or two standard metal muffin pans with high-quality paper liners (yields 12 to 16 muffins depending on the pan size).

In a medium ceramic bowl, vigorously whisk together the all-purpose flour, pumpkin pie spice, baking soda, baking powder, and kosher salt. This ensures the leavening agents are perfectly distributed, guaranteeing an even rise.

In a large mixing bowl, thoroughly mash the ripe bananas until virtually liquid.

Stir the large eggs, vegetable oil, canned pumpkin puree, granulated sugar, and packed dark brown sugar into the mashed bananas, whisking until the wet ingredients form a smooth, unified emulsion.

Pour the dry flour mixture directly into the wet pumpkin and banana emulsion.

Using a wooden spoon or rubber spatula, gently fold the ingredients together only until just combined. Do not overmix, as overworking the gluten will result in a dense, tough crumb.

Use a heavy-duty ice cream scoop to portion the thick batter evenly into the prepared muffin cups, filling each nearly to the top to encourage a high dome.

Bake in the preheated oven for 20 to 22 minutes. The muffins are finished when the tops spring back gently to the touch and a wooden tester inserted into the center comes out perfectly clean.

Allow the muffins to cool in the pan for 5 minutes before transferring them to a wire rack. Serve warm.