Preheat oven to 350.
Combine flour and powdered sugar in a medium bowl, whisking to remove any clumps. Set aside.
Pour egg whites into bowl of stand mixer; add cream of tartar and vanilla. Beat on medium speed until soft peaks form.
Gradually add sugar, a tablespoon at a time, beating until stiff peaks form. Remove bowl from stand mixer.
Sprinkle one-fourth of the flour/powdered sugar mixture over the egg whites. Fold gently.
Repeat, adding the flour mixture in fourths.
Pour into an ungreased 10-inch tube pan.
Use a spatula or butter knife to cut through the batter and remove air pockets.
Bake on the lowest oven rack for 40-45 minutes. The top of the cake will spring back when touched lightly, if the cake is done.
Immediately invert cake onto your chosen base; cool thoroughly.
Remove cake from pan. You will need to use a knife to loosen the cake from the sides of the pan.