Finely grate peel from 2 lemons (save for cake), then squeeze out 1 cup juice. In a medium large sauce pan, whisk sugar with cornstarch. Whisk in lemon juice, eggs and egg yolks until blended. Set over medium heat, stirring constantly until mixture boils, 7 - 10 minutes (cornstarch will prevent it from curdling).
Remove from heat and stir in cubes of butter until combined. Sieve into a bowl. Place a piece of plastic wrap on surface and refrigerate until cold.
Prepare angel food cake as per instructions, folding in lemon peel at the end. Bake and cool as directed on package. When cake is cooled, cut horizontally in half.
Place bottom layer on a cake plate and spread with about half of the lemon curd. Place top of cake on curd. Spread top with a layer of curd (there will likely be leftover curd).