- 3 tablespoons extra-virgin olive oil
- 1 fresh swordfish or tuna steak, cut 3/4-inch (2 cm) thick (about 1 pound/500 grams)
- Sea salt and freshly ground black pepper to taste
- 1 small onion, minced
- 1 rib celery, cut into thin slices
- 1 (28-ounce/765-gram) can peeled Italian plum tomatoes in juice or one (28- ounce/765-gram) can crushed tomatoes in puree
- 1/4 teaspoon crushed red peppers (hot red pepper flakes), or to taste
- 1/3 cup (80 ml) drained pitted green olives
Preheat the oven to 450 degrees F (230 degrees C/gas mark 9). In a large skillet, heat the oil over moderately high heat until hot but not smoking. Add the swordfish and brown lightly, 2 to 3 minutes per side, seasoning each side with salt and pepper after browning. Using a large flat spatula, transfer to a baking dish just large enough to hold the fish. Set aside.
In the same skillet, cook the onion and celery over moderate heat until translucent, 4 to 5 minutes. If using whole canned tomatoes, place a food mill over the skillet and puree the tomatoes directly into it. Crushed tomatoes can be added directly from the can. Add the crushed red peppers. Stir to blend, cover, and simmer until the sauce begins to thicken, about 15 minutes. Stir in the olives. Taste for seasoning.
Spoon the sauce over the fish. Cover the dish with foil, place in the centre of the oven, and bake for 30 minutes. To serve, quarter the fish, remove the skin, and transfer to warmed individual dinner plates. Use a slotted spoon to transfer the sauce to the plates, since the sauce tends to thin out while baking.