Preheat oven to 350 degrees F (175 degrees C). Lightly grease one 9x13 inch baking dish.
Place potatoes in bottom of prepared dish.
Combine the 1/2 cup butter, condensed soup, cheese, sour cream, salt and onion; mix well and pour over potatoes. Top with crushed corn flakes and drizzle with 1/2 cup melted butter.
Bake uncovered at 350 degrees F (175 degrees C) for 45 minutes.