- Sugar—For the best angel food cake, you’ll need to pulse the sugar in a blender or food processor. This extra step is crucial! Since the cake batter is so light and delicate, coarse sugar is too heavy, while powdered sugar dissolves too quickly into the egg whites. Those super-fine granules are just the right size to dissolve easily into the egg whites.
- Cake flour—There’s no substitution here; cake flour is an absolute must for this angel cake. It has a lower protein percentage than all-purpose flour, which gives you that light-as-air texture. Unfortunately, all-purpose flour will give you a more bread-like texture.
- Eggs — This recipe doesn’t call for any leaveners. Instead, this cake gets its rise from egg whites alone! It’s important to be very careful when separating the egg whites from the egg yolks. Even just a drop of egg yolk can cause this cake to fall. Carton egg whites don’t aerate or whip up as well, so stick with fresh. Save the egg yolks to make a delicious custard or lemon curd to serve with the cake. Or make a pound cake or egg noodles.
- Cream of tartar—Cream of tartar is an acid that helps stabilize the meringue. Without it, the cake will collapse.
- Sourdough Discard—Fresh sourdough discard, no more than 1-2 days old, is best for this recipe. You’ll also want to use room-temperature discard, as it’s so much easier to gently mix into the angel cake batter without deflating it. Sourdough discard from the fridge or an active sourdough starter is too thick, and it’ll take longer to incorporate. Runny, room-temperature discard mixes in nicely.
- Salt – A pinch of salt helps balance the sweetness and brings out the flavor of the other ingredients.
- Vanilla Extract – Pure vanilla extract is strongly recommended here over imitation for the best flavor.
