Preheat oven to 375. Beat the egg whites until foamy, add the salt and cream of tartar, and beat until soft peaks form. Add the vanilla, then gradually add the sugar, beating until stiff. Sift the flour over the whites in two batches. Mixing briefly with the mixer after each addition, only until blended.
Bake in an ungreased 10-inch tube pan for 40-45 minutes, until a straw comes out clean. Invert the pan on a rack and let the cake cool completely before removing from the pan.