Preheat oven to 350°F. Grease a 9x13-inch baking pan with butter or nonstick cooking spray. Set aside.
In a large bowl, stir together the apple pie filling, caramel ice cream topping, ground cinnamon, ground nutmeg, ground allspice, and ground cardamom until well-combined. Pour the filling into the prepared baking dish.
40 ounces apple pie filling, ¾ cup caramel ice cream topping, 1 teaspoon ground cinnamon, 1 teaspoon ground nutmeg, 1 teaspoon ground allspice, ½ teaspoon ground cardamom
Sprinkle the walnuts evenly over the apple filling.
⅔ cup chopped walnuts
Sprinkle the cake mix over the walnuts and filling and spread it out evenly.
15.25 ounces yellow cake mix
Cut the unsalted butter into thin squares and cover the entire top of the cake with the squares of butter.
1 cup unsalted butter
Bake for 45-50 minutes, or until there are no more dry spots on top of the cake and the filling is warmed through and bubbling.
Drizzle additional caramel topping over the cake and serve warm with a scoop of vanilla ice cream and sprinkle of walnuts if desired.
1 pint vanilla ice cream