In a medium bowl, measure the gluten free flour mix, pumpkin pie spice, baking powder, baking soda and salt. Lightly mix it together with a whisk. Set aside.
In the bowl of a stand mixer, add the butter and brown sugar and beat well, about 1 minute.
Add the eggs, one at a time, beating for 30 seconds after each addition.
In with the sugar mixture, add the pumpkin, buttermilk and vanilla. Beat for 2 minutes on medium, until the mixture is combined.
All at once, add the flour mixture to the pumpkin batter. Mix the flour mixture in until combined, about 1 minute.
Using a rubber spatula, fold in the pecans.
Set batter aside to rest for 30 minutes.
Preheat oven to 350 F. Spray an 8” x 4.5” loaf pan evenly with cooking spray.
Scrape the batter into the prepared pan. Smooth out the top slightly.
Bake in the preheated over until a toothpick inserted in the center comes out clean. Start checking it at about 50 minutes in. The gluten free pumpkin bread could take up to 1 hour and 15 minutes, so extra time is not uncommon.
Cool for 10 minutes before removing from the pan to a wire rack to cool completely.
Make sure all ingredients are at room temperature.
Use a stand mixer for the easiest way to mix the batter.