I often come across recipes that require cake flour rather than all purpose flour. I don't always have it in the pantry, so I'm posting a simple recipe for Cake Flour below. Love this wonderful retro advertisement that offers up the recipe (without the sifting).
How to make Cake Flour
In a cup measure, add 2 Tbsp cornstarch, then fill the cup up with flour. So basically for every cup of flour, you take out two Tbsp of the flour and add 2 Tbsp cornstarch. Sift before adding to your other ingredients. I actually sift several times for better aeration.
Want to buy the best cake flour? I like King Arthur Flour's cake flour. It's unbleached flour.