Portuguese Marinated TunaPortugal is a country that loves its seafood bathed in the deep green olive oil made from the fruits of its own rolling hills. Hot red pepper, an influence of the Moors, and tart lemon and capers punch up the flavor in this dish. As is typical of Portuguese cuisine, this succulent fish is blessed with bright green chopped cilantro just before serving. I guarantee you will fall in love with this dish.
Using a food processor or blender, purée all marinade ingredients except for the fish. Place the tuna in a nonreactive dish. Pour the marinade over and turn the fish to coat on all sides. Cover and refrigerate overnight, or for at least 4 hours, turning once.
To cook the fish, preheat the broiler or prepare the grill. While waiting for your heat source to warm, pour off the marinade into a small saucepan and bring to a boil. Cook 1 minute until it reduces slightly to form a sauce; if the sauce is too thin, then add a splash more wine or lemon juice. Turn off the heat and stir in the reserved chopped fresh cilantro. Set aside.
Broil or grill the tuna steaks on high heat, close to the flame, turning once during cooking. Base the total cooking time on the Canadian Rule (ten minutes to the inch) or, if you prefer your tuna rare, undercook it slightly. Serve the tuna steaks with the sauce poured over or around them and garnish with cilantro sprigs.