Cast iron is an ideal cooking vessel. It's a slow, even conductor of heat, so food browns beautifully. You can bake in it, fry in it, saute and sear in it. In fact, one of the best ways to cook a thick filet of cod or tuna, or even sea scallops, is to get the skillet very hot, brush the fish with a tiny bit of oil, then sear the fish or scallops for just two minutes on each side, so that it gets brown and crisp outside but stays moist inside.