In a plastic bag combine all ingredients except the tuna. Mix the marinade in the bag until combined and add the tuna, coating it completely. Seal the bag, refrigerate, and let the tuna marinate for 1 to 2 hours, turning it occasionally.
Preheat a grill, or broiler with rack in the top position.
Brush the grill with vegetable oil. Discard the marinade and grill the tuna (or broil it on a rack set in a baking pan) for 3 minutes on each side until medium rare.
Swordfish can also be prepared this way.
Copyright Leslie Glover Pendleton, author of Simply Shrimp, Salmon, and (Fish) Steaks