Preheat oven to 375° F. Grease a standard muffin pan or line with baking cups.
In a medium mixing bowl, whisk together the gluten free flour blend, baking soda, baking powder, pumpkin pie spice, and salt.
In a large mixing bowl, whisk together oil, eggs, sugars, and vanilla until combined.
Add pumpkin puree and milk to sugar mixture and whisk until combined.
Stir the flour mixture into the pumpkin mixture until just combined.
Divide the batter evenly among the muffin cups.
Bake for 18-22 minutes until a wooden pick inserted into the center of a muffin comes out clean.
Allow to cool for 5 minutes in the pan, then transfer to a wire rack to cool completely.
Notes
Be sure to use pumpkin puree, not pumpkin pie filling. Pumpkin pie filling has sugar and spices in it and will make the muffins too sweet.
When adding the dry ingredients to the wet ingredients, use a wooden spoon or spatula to stir everything together. Stirring or folding the mixture by hand will prevent overmixing the batter. Overmixing may lead to muffins that are tough.
Use a large scoop to fill the muffin cups with batter. This will keep the muffins similar in size and ensure even baking time.
Cool the baked muffins for 5 minutes and then remove them from the pan to a wire rack. Using a rack helps the muffins cool more quickly.