1) Preheat oven to temperature of 350 degrees.
2) Melt the margarine over moderate heat in a small skillet.
3) Add the apple, onion, raisins, curry and salt and cook, occasionally stirring, till the apples are tender.
4) Use non-stick cooking spray to spray a shallow 1-quart casserole.
5) In the casserole, arrange the fillets and top with the onion mix.
6) Bake in preheated oven for about 15 to 20 minutes, till the fish easily flakes when touched with a fork.