Ingredients

Active time 10 minutes, start to finish 25 minutes

3/4 pound Italian fry peppers (light green)
Two 3/4-pound sushi-grade tuna steaks (1-inch-thick)
1 1/4 teaspoons salt
1 teaspoon black pepper
1 1/2 teaspoons fresh lemon juice
1/2 teaspoon Dijon mustard
1/4 cup olive oil
1 1/2 tablespoons small capers in brine, drained and chopped
2 tablespoons chopped fresh flatleaf parsley

Prepare gas grill for cooking over direct high heat (see note.) While grill heats, cut peppers lengthwise into quarters, discarding stems and seeds. Trim ends so that quarters lie flat.
Sprinkle tuna all over with 1 teaspoon salt and 1/2 teaspoon pepper. Cook tuna and peppers on lightly oiled grill rack, turning over once, until tuna is pink only in center and peppers are just tender, 4 to 6 minutes total (peppers may take longer than tuna). Transfer tuna and peppers as cooked to a serving plate.
While tuna cooks, whisk together lemon juice, mustard and remaining 1/4 teaspoon salt and 1/2 teaspoon pepper in a small bowl, then add oil in a slow stream, whisking until emulsified. Whisk in capers and parsley.
Serve tuna topped with peppers and caper vinaigrette.
Makes 4 servings.

Directions

Note: If you don't have a gas grill or aren't able to grill outdoors, cook tuna on a lightly oiled well-seasoned large (2-burner) ridged grill pan over moderately high heat, turning once, 4 to 6 minutes total.