Preheat oven to 400 degrees. Whisk together flour, walnuts, sugar, brown sugar, cinnamon, nutmeg and a pinch of salt. Pour butter over dry ingredients and mix with a fork to break apart large chunks. Set aside.

Divide apple pie filling between (2) 6" cast iron skillets or place all apple pie filling in casserole dish. Top with dry mixture.

Place skillets or casserole dish on baking sheet and bake until topping is browned, about 35 minutes. Serve with a scoop of vanilla ice cream!