3 tablespoons reduced-sodium soy sauce
2 tablespoons lemon juice
2 tablespoons oil; more for brushing pan
1 garlic clove, minced
1/2 teaspoon sugar
1/2 teaspoon freshly ground black pepper
1/4 teaspoon salt
tuna steaks, 3/4 to 1 inch thick.
In a large plastic bag combine soy sauce, lemon juice, 2 tablespoons vegetable oil, garlic, sugar, pepper and salt. Add tuna steaks, coating well with marinade. Seal bag, and refrigerate at least 30 minutes, and up to 2 hours.
Place a ridged grill pan over medium-high heat for about a minute. Brush pan with oil. Remove fish from marinade, discarding liquid, and add to pan. Cook to taste (3 minutes on each side for medium-rare). Serve immediately.