Stir cake mix and melted butter together, then press some of it into a buttered square baking pan to form the crust.
Beat cream cheese, some of the lemon pie filling, an egg, powdered sugar, and salt together, then spread over the crust.
Top with the remaining lemon pie filling and crumble the rest of the cake mix over the top.
Bake until browned around the edges, then let cool for at least 45 minutes before serving.
