Remove the backbones from the fish without cutting
them in half, or have your fish dealer remove them.
Preheat broiler. In a shallow baking dish large enough
to hold the fish laid out flat in one layer, combine
the oil, lemon juice, salt, black pepper and onions.
Place the mackerel in this marinade, flesh side down
for 15 minutes, then turn them over for another 15
minutes. Brush the broiler grill with 1 tablespoon of
melted butter and oil and place the mackerel on it,
skin side down. Grill only one side about 3" from
heat, basting from time to time with remaining butter
and oil. In 10 to 12 minutes they should have turned a
light golden color and their flesh should flake easily
when prodded with a fork. Serve at once, accompanied
by butter-steamed new potatoes and tomato or
horse-radish butter. (See recipes.)
