Preheat the oven to 350 degrees F. Lightly coat a jelly roll pan with nonstick cooking spray.
In a large mixing bowl or stand mixer, beat the ripe banana until smooth. Add the vegetable oil and eggs, stirring until combined.
Mix in the sugar and pumpkin puree. Beat on low speed for 1–2 minutes, until the sugar is dissolved.
Add the gluten free flour, sea salt, baking powder, cinnamon, and pumpkin pie spice. Stir until the batter is smooth and no streaks of flour remain.
Pour the batter into the prepared pan and spread evenly. Bake for 25–30 minutes, or until a toothpick inserted in the center comes out clean.
Remove from the oven and let the bars cool completely before frosting.
For the frosting, beat the softened cream cheese and butter together until smooth. Add powdered sugar, milk, and vanilla. Mix until creamy with no lumps. (If your cream cheese or butter wasn’t fully at room temperature, small lumps may remain, but the frosting will still taste delicious.)
Spread the frosting evenly over the cooled bars with an offset spatula. Refrigerate until set. Once cut, store bars in an airtight container in the refrigerator to keep them fresh.
Notes
Note 1: If you do not have a banana, use ½ cup of vegetable oil for a total of 1 cup. The riper the banana, the higher the fructose content, which may be an issue for some on a low FODMAP diet.Note 2: Use any neutral tasting oil such as avocado oil.Note 3: Use pure pumpkin, not pumpkin pie filling. Roasting your own pumpkin is also an option. Drain any excess liquid before using. I have not tested this option. Note 4: Recipe was tested using Bob’s Red Mill 1-to-1 in the light blue bag. Pan Sizes:
Jelly Roll Pan (15 x 10 inches, 1-inch sides): Yields classic thin pumpkin bars with the perfect layer of frosting.
9x13 Baking Pan: Makes thicker, more cake-like bars. Add extra baking time.
Half Sheet Pan (18 x 13 inches): Produces very thin bars that bake quickly. Double the frosting so you have enough to cover the surface.