Cake Flour

Cake flour is produced from the endosperm portion of the wheat kernel of soft wheat varieties. It is high in starch and has a low protein content, which means that it contains very little gluten, making it suitable for cake recipes.
If cake flour is not available, cornstarch makes a good substitute. All-purpose flour can also be used although the results will not be quite as light and airy. Subtract 2 tablespoons from each cup specified in the recipe when using all-purpose flour as a substitute for cake flour.