Prep for baking. Heat oven to 350°F and adjust rack to the middle. Line a baking sheet with parchment paper and grease the parchment.
Mix dry ingredients. Combine 2 cups gluten-free flour, 1 1/2 teaspoons baking powder, 1 teaspoon baking soda, 1/2 teaspoon salt, and 1 teaspoon cinnamon in a medium bowl and whisk to break up any lumps and incorporate ingredients.
Finish the dough. Whisk 2 eggs, 1/2 cup granulated sugar and 1/2 cup brown sugar in a large bowl with a whisk until lightened in color, about 2 minutes. Whisk in 1/2 cup oil, 1 cup pumpkin puree and 1 teaspoon vanilla until blended. Add flour mixture, and mix with a rubber spatula until incorporated. Dough will be very soft, like a little thicker than muffin batter.
Bake. Scoop tablespoon-sized mounds of dough onto the baking sheet, about an inch apart. Smooth the tops with a butter knife and bake until firm on top and just starting to brown on the bottom, about 12-15 minutes.
Cool. Remove cookies to a wire rack and let cool completely.
Dust. Once completely cool, dust the tops with powdered sugar.