Grilled Tuna Sandwiches with Chile Aioli

2 tablespoons chopped fresh cilantro
6 tablespoons low-fat mayonnaise
1 teaspoon ground ancho chile pepper
1 teaspoon grated lime rind
1 teaspoon fresh lime juice
1/4 teaspoon ground chipotle chile pepper
5 teaspoons olive oil, divided
4 (1/4-inch-thick) slices Oso Sweet or other sweet onion
1 red bell pepper, seeded and quartered
1/2 teaspoon salt, divided
4 (5-ounce) tuna steaks (about 3/4 inch thick)
1/4 teaspoon ground cumin
1/4 teaspoon freshly ground black pepper
4 (2-ounce) sandwich buns
4 red leaf lettuce leaves

Heat a grill pan over medium-high heat.

Combine first 6 ingredients in a small bowl.

Brush 3 teaspoons oil evenly over onion and bell pepper; sprinkle with 1/4 teaspoon salt. Place onion and bell pepper on grill pan; cook 3 1/2 minutes on each side or until tender. Remove from pan; keep warm.

Brush 2 teaspoons oil evenly over tuna; sprinkle with remaining 1/4 teaspoon salt, cumin, and black pepper. Place tuna on grill pan; cook 3 1/2 minutes on each side or until medium-rare or desired degree of doneness.

Split buns in half horizontally. Spread mayonnaise mixture evenly over cut sides of buns. Top bottom half of each bun with lettuce, 1 bell pepper quarter, 1 onion slice, and 1 tuna steak. Cover with top halves of buns.
from Cooking Light