Preheat oven to 350°F (175°C). Line a baking sheet with parchment paper or lightly grease it.
Prepare dry ingredients: In a separate bowl, whisk together 2 ½ cups + 2 tbsp gluten-free flour (with xanthan gum), 1 tsp baking powder, 1 tsp baking soda, ¼ tsp salt, 2 tsp pumpkin pie spice, and ½ tsp cinnamon.
Prepare wet ingredients: In a large mixing bowl, cream together ½ cup (1 stick) softened butter, ¾ cup brown sugar, and ¾ cup sugar until light and fluffy using a hand mixer or stand mixer. Add in 1 large egg, 1 cup pumpkin puree, 2 tsp vanilla extract, and 1 tsp apple cider vinegar. Mix until fully combined.
Combine ingredients: Gradually add the dry ingredients to the wet mixture, mixing until just combined. If the mixture is still too wet, add one tablespoon of gluten-free flour at a time until it's no longer too sticky.
Scoop the dough: Use a cookie scoop for small cookies or a ice cream scoop for large cookies. Scoop and roll in a ball and place onto the prepared baking sheet, spacing them about 2 inches apart. Press down until flat.
Bake: Bake the cookies for 12-14 minutes, or until they are set and lightly golden around the edges.
Cool: Let the cookies cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely