Preheat oven to 325 F.
Sift flour, 1 cup of sugar, baking powder, and spices into a large bowl.
Add the oil, egg yolks, pumpkin puree, and vanilla.
Beat with a whisk or using a mixer on low speed until batter is smooth.
In another large bowl, beat egg whites and cream of tartar until the mixture forms soft peaks.
Gradually beat the remaining 1/3 cup sugar into the egg whites, blending until very stiff peaks form.
Use a rubber spatula to carefully fold one quarter of the egg white mixture into the pumpkin batter until just mixed. Repeat three more times with the remaining egg whites, folding until no streaks remain.
Pour the batter into an ungreased, 10-inch angel food cake pan and bake for 50-55 minutes or until a cake tester inserted into the center of the cake comes out clean.
Remove from oven and cool, inverted, for roughly two hours.
When the cake has cooled completely, run a table knife or thin spatula around the edges, gently loosening the cake from the pan before turning it out onto a plate.
Serve with a dusting of powdered sugar.