Preheat an outdoor grill for medium-high heat and lightly oil the grate with cooking spray.
Brush tilapia with lime juice and sprinkle with lemon-pepper.
Cook on the preheated grill, covered, until fish flakes easily with a fork, 5 to 6 minutes.
While fish is grilling, combine mayonnaise, Dijon mustard, and honey in a bowl. Spread over bottom half of buns and top with lettuce and tomato. When fish is finished, place on prepared buns and enjoy!