Combine lemon juice, oil, lemon peel and Knorr® Chicken flavor Bouillon in small microwave-safe bowl. Evenly coat chicken with 2 tablespoons Bouillon mixture.
Grill or broil chicken, turning once, until chicken is thoroughly cooked, about 20 minutes. Microwave remaining Bouillon mixture at HIGH 30 seconds; stir.
Remove chicken from bone, then slice. Toss lettuce, tomato, cucumber and onion with warm Bouillon mixture in large salad bowl or platter, then top with chicken. Garnish, if desired, with chopped fresh cilantro. Serve with rolls.