Preheat the oven to 350 degrees F and line a pullman pan or 9x5 loaf pan with parchment paper.
In a medium bowl, combine the flour, baking powder, baking soda, salt, and pumpkin spice. Set aside.
In a separate large bowl, whisk together the brown sugar, granulated sugar, and oil.
Then, whisk in the eggs and vanilla, and lastly the pumpkin purée.
Add the dry ingredients to the wet and whisk until fully combined and smooth.
Pour the batter into the prepared pan and smooth out the top. Use a knife to draw a line down the center in order to encourage the batter to split down the middle as it bakes.
Bake the pumpkin bread for 1 hour to 1 hour 10 minutes or until a toothpick inserted comes out with a few moist crumbs. Tent with foil around the 40 minute mark to prevent it from getting too dark.
Allow the pumpkin bread to cool in the pan for about 10 minutes, then transfer to a wire rack to cool completely.