All purpose flour is the standard flour for home baking, but a glance down a well equipped grocery store baking aisle is enough to tell you that there are many other types of flour available for baking. Cake flour is one of them and, if you like to bake, it should be a staple in your kitchen. Cake flour is a low protein flour that is made from soft winter wheat. It has a protein content of about 8% and is usually bleached, which gives it a very fine texture and a very light color. Because it has such a fine texture, cake flour should be sifted before incorporating it into a recipe to prevent clumping.
As the name suggests, cake flour is great for making cakes and other baked goods because it gives you a very tender result. This is because it has such a low protein content compared to other flours (all purpose is usually around 10%) and less gluten forms when you mix it into a batter, producing a cake with a fine, soft, even crumb. Although all purpose flour can yileld a great cake, there is generally a noticeable difference in the texture between a cake made with all purpose flour and one made with cake flour. You can make any kind of cake with cake flour, but it is commonly flour in white cakes and in angel food cakes, both of which are known for having a light texture.
There are many recipes that specifically call flour cake flour, but you can substitute it into a recipe that calls for all purpose flour, too. Use 1 cup of cake flour plus 2 tablespoons for each cup of all purpose flour called for. By the same token, you can substitute all purpose flour for cake flour in a pinch by using 1 cup of all purpose flour minus 2 tablespoons for each cup of cake flour called for in a recipe. Still, it is best just to use cake flour instead of approximating it if you want to get the best results from your recipes.