1. All-purpose flour + cornstarch
2 tbsp
cornstarch
Best swap: All-purpose flour + cornstarch. Use ⅞ cup all-purpose flour (1 cup minus 2 tbsp) plus 2 tbsp cornstarch per 1 cup.
Cake flour is low in protein, which gives cakes a soft, fine crumb. Swapping a little of the flour for cornstarch lowers the protein of plain flour and mimics it closely.
For 1 cup of cake flour, measure 1 cup of all-purpose flour, take out 2 tablespoons, and replace them with 2 tablespoons of cornstarch. Sift several times so it blends evenly.
Its low protein content means less gluten forms, giving cakes a softer, finer and more tender crumb than all-purpose flour would.