This recipe is from a Cook's Illustrated article by Susan Logozzo about perfecting the lemon bar. NOTE: The lemon filling must be added to a warm crust. The 30 minute chilling time and 20 minute baking of the crust should allow plenty of time to prepare the filling. If not, make the filling first and stir to blend just before pouring it onto the crust. Prep time includes 30 minute chilling time for crust.