The lemon flavor of the Lemon Bars comes from a mixture of lemon juice, lemon zest, sugar, eggs (not just egg yolks like in lemon curd, you are using the entire eggs) and a small amount of all-purpose flour to thicken the mixture as it bakes. This filling would also work as a double layer cheesecake topping. Bake the cheesecake layer first for 30 minutes in a 9 x 13 pan (with deep edges) using this New York Cheesecake recipe, then top with lemon filling and bake an additional 30 minutes.