Preheat oven to 350°F (175°C).
Coat a 9x13-inch baking pan with cooking spray.
Place apple pie filling in an even layer on the bottom of the pan.
Pour caramel sauce over the apples in an even manner.
Sprinkle the cake mix evenly over the apples and caramel.
Pour melted butter over the cake mix, spreading it evenly.
Sprinkle the chopped walnuts evenly over the mixture.
Bake in the preheated oven until the cake is golden brown and the filling is bubbling through to the top, approximately 50 to 55 minutes.
Let it cool for at least 15 minutes before serving. Can be enjoyed warm or at room temperature.