Preheat the oven to 350℉ degrees. Grease a 9×5-inch loaf pan with butter or non-stick spray, then line it with parchment paper so the loaf lifts out cleanly.
Sift the flour, baking soda, baking powder, salt, cinnamon, ground ginger, ground nutmeg, ground cloves, and ground allspice into a large bowl.
In a medium bowl, beat together the sugar, pumpkin puree, vegetable oil, eggs, and vanilla.
Pour the pumpkin mixture into the flour mixture and fold with a spatula just until no flour pockets remain.
Pour into the prepared loaf pan, spreading evenly.
Bake for 50 to 60 minutes, until a toothpick or knife inserted in the center comes out clean.
Let cool in the pan on a rack for 10 minutes, then use the parchment to lift the loaf onto the rack to cool completely (about 1 to 2 hours).