Preheat the oven to 350°F (175°C) and grease a 9x13-inch baking dish.
Spread the lemon pie filling evenly over the bottom of the dish.
In a bowl, beat the cream cheese, sugar, vanilla extract, and milk until smooth. Spread the mixture over the lemon pie filling.
Sprinkle the dry lemon cake mix evenly over the top.
Drizzle the melted butter over the cake mix, ensuring as much of the surface is covered as possible.
Bake for 35-40 minutes or until the top is golden brown and bubbly.
Let cool slightly before serving. Enjoy warm or chilled.