Preheat the oven to 350°F. Generously grease a 12-cup Bundt pan.
Whisk together gluten-free flour, pumpkin pie spice, baking soda, baking powder, and salt in a large bowl.
In a stand mixer, beat shortening, granulated sugar, and brown sugar for 1-2 minutes until creamed.
Add oil, vanilla, and eggs to the mixer and mix until smooth, scraping the bowl.
With the mixer on low, add ⅓ of the dry ingredients, then ½ the pumpkin, mixing after each addition.
Repeat alternating dry ingredients and pumpkin until combined. Pour batter into the prepared Bundt pan and smooth the top.
Bake for 60-70 minutes, or until a toothpick comes out clean.
Cool in the pan for 20-30 minutes, then invert onto a wire rack to cool completely before frosting.