In a large, clean mixing bowl, add the 1 ½ cups of egg whites. Beat them with an electric mixer on medium speed until they become foamy.
Sprinkle the 1 ½ teaspoons of cream of tartar into the egg whites. Gradually add the 1 cup of granulated sugar to the egg whites, a few tablespoons at a time. Continue beating until stiff peaks form.
Add the ½ tablespoon of vanilla extract and ¼ teaspoon of salt to the egg whites. Beat for another 30 seconds to incorporate these flavors. Sift together the 1 ½ cups of powdered sugar and 1 cup of cake flour onto a piece of parchment paper.
Gradually fold the sifted flour mixture into the egg whites with a rubber spatula. Once the dry ingredients are fully incorporated, gently spoon the batter into an ungreased tube pan.
Bake the cake in your preheated oven for about 45 minutes, or until the top is golden brown and the cake springs back when lightly touched.
Immediately after removing the cake from the oven, invert the pan (flip it upside down) onto a glass bottle or onto cans. Allow the cake to cool completely while inverted. Once it’s cooled, run a knife along the edges of the pan to release the cake.