Preheat and Prepare: Preheat your oven to 350°F (175°C). Do not grease the tube pan. This is critical, as the batter needs to cling to the sides of the pan to climb and achieve its height.
Whip the Egg Whites: In a large, clean bowl, combine the egg whites, cream of tartar, and salt. Begin whipping on medium speed until foamy.
Gradually Add Sugar: Slowly increase the speed to high and gradually add ½ cup of the granulated sugar, about a tablespoon at a time, while continuing to whip. Continue whipping until stiff, glossy peaks form. This means when you lift the whisk, the peaks stand straight up without drooping.
Incorporate Flavouring: Gently fold in the vanilla extract.
Combine Dry Ingredients: In a separate bowl, sift together the cake flour and the remaining ½ cup of granulated sugar at least three times. This aerates the flour and sugar mixture and ensures it’s well combined, which is vital for an even texture.
Fold in Dry Ingredients: Gently fold the sifted dry ingredients into the whipped egg whites in three additions. Use a rubber spatula and a light, lifting motion to incorporate the flour without deflating the egg whites. Be careful not to overmix; stop as soon as no streaks of flour remain.
Bake: Carefully spoon the batter into the ungreased tube pan. Run a knife or spatula through the batter to release any large air pockets. Bake for 35-45 minutes, or until the cake is golden brown, springs back when lightly touched, and a wooden skewer inserted into the center comes out clean.
Cool Upside Down: Immediately upon removing from the oven, invert the pan onto its “feet” or over the neck of a bottle. This allows gravity to help prevent the delicate cake from collapsing as it cools. Let it cool completely, which can take 1-2 hours.
Release the Cake: Once completely cool, run a thin knife or offset spatula around the edges of the pan and the centre tube to loosen the cake. Invert it onto a serving plate.