La Narval by Don Gastronom. Mackerel Fillets in Tomato Sauce. Filetes de Caballa en Salsa de Tomate. One tin of 120g (4.23oz). Product of Spain. Clean mackerel fillets, with no bone, in tomato sauce. After being cooked in seawater, La Narval dries the mackerel a little bit so that when it gets in contact with the sauce, it gets re-hidrated again increasing its taste and texture. Exquisite fish high in B6 and B12 vitamins.