To prepare marinade, combine lime juice, orange juice, rum, mint, coriander, and garlic in a large ziptop bag. Add chicken and move the chicken around in the bag to coat it well with marinade. Let chicken sit on counter for 20 minutes.
Prepare Mojito Mayonnaise. Combine all ingredients in a small bowl and refrigerate.
Prepare grill or heat grill pan over medium-high heat. Coat with cooking spray.
Remove chicken from marinade and place on grill. Discard marinade. Place onion slices on grill.
Grill 4 minutes each side, or until chicken is cooked through. Grill onions until soft.
Remove chicken and onion from grill. Sprinkle chicken with salt and pepper.
Spread 1 tablespoon of mayonnaise mixture on bottom of each bun. Top with chicken, onion, lettuce, and tomato.
This recipe originally appeared on spicysouthernkitchen.com