sprinkle fillets on both sides with salt and pepper. Place fillets in a single layer in a greased baking dish 12x8 inches. Arrange tomatoes over top of fillets. Sprinkle with salt and pepper. Blend flour into margarine. Add milk gradually and cook until thick and smooth, stirring constantly. Remove from heat and stir in wine and basil. pour sauce over top of tomatoes. Bake in a 350 oven for 25-30 minutes or until fish flakes easily.