Storage: Store the cake in the refrigerator due to the cream cheese frosting. Bring to room temperature for 30 minutes before serving for the best texture.
Substitutions: If you cannot find superfine sugar, you can pulse regular granulated sugar in a food processor for 10 seconds.
Tip: Ensure all ingredients, especially egg whites and butter, are at room temperature to achieve a smooth, airy batter.
Variation: Add a teaspoon of lemon zest to the milk mixture for a citrusy twist.