I don't know about you, but when a cake or other baking item requires cake flour, I always pass on the recipe. Buying cake flour for one item seems to be a little costly for one recipe. So here's a tip. You can use regular flour to make a particular recipe that requires cake flour. For every cup of cake flour that is required in a recipe you can substitute with the following. Measure out 1 cup of flour and remove 2 tablespoons of the flour. Replace those 2 tablespoons of flour with 2 tablespoons of cornstarch. If you require more flour do the same thing. Make sure you sift the flour and cornstarch so it is well incorporated. I love this tip. I've now used it several times and it works great.
Source: Sally's Baking Addiction