Heat oven to 350°F.
Using an egg separator, separate one of the eggs into a small bowl or measuring cup. Then transfer egg white to a large bowl. Repeat with remaining eggs (this keeps any yolk from accidentally getting into all your whites). Discard yolks. Let egg whites warm to room temperature. Add cream of tartar and salt to egg whites.
Beat egg whites until frothy. Gradually beat in superfine sugar, 2 tablespoons at a time, until stiff but glossy peaks form, about 5 to 7 minutes. Beat in vanilla extract.
Fold flour into egg whites in two additions, until incorporated. Spoon batter into an ungreased 10-inch tube pan.
Bake at 350°F for 35 to 40 minutes, until top has risen very high and is lightly browned and cracked. Remove from oven and immediately invert onto baking sheet or neck of bottle. Cool completely.