Eight anchovy fillets sound like far too many until they hit hot oil and disappear. Mashed to a rough paste with rosemary and garlic and spread thickly across swordfish steaks, nothing about the finished steak tastes of anchovy, only of something savory you cannot quite place. Twenty minutes, four steaks, four ingredients.
Buy the steaks a full inch thick and do not compromise on it. A thick steak stays firm enough to hold that salty paste on top of it, and it buys the crust the time it needs in a 425°F oven. Thinner fish reaches the middle long before the surface has colored, so you get the taste without the finish. Heat the sheet pan along with the oven and brush oil across it before the steaks land, because lean fish welds itself to bare hot metal and tears when you go to lift it.
Cooked to 145°F, swordfish comes out opaque and firm all the way through, closer to a piece of meat than to a flaking white fillet, and you eat it with a knife. Give the steaks five minutes to rest, then spoon whatever collected in the pan back over the top. Thick cod loin or halibut takes the same paste when the counter has no swordfish.
