Apple dump cake (a.k.a. panic)

1 can apple pie filling (not sliced apples)
1 package yellow cake mix (1 layer)
1 stick margarine or butter, melted
? cup walnuts, chopped

Pour pie filling into a buttered 8x8x20inch baking pan. Cover with dry cake mix. Drizzle melted butter or margarine over cake mix. Sprinkle with nuts. Bake at 375 degrees F for 45 minutes or until brown. Serve warm or cold. Can be reheated