Wash and dry the fillets. Sprinkle with salt and lemon juice. Set aside for a few minutes to marinate. Combine the yoghurt with the rest of the ingre¬dients. Place the fish in a shallow baking dish. Make two deep gashes across the fillets. Pour the yoghurt mixture over the fish and leave to soak for several hours. Bake in a moderate oven (375° F. — Gas Mark 5) for 30 minutes.