1. Combine the marinade ingredients in a shallow glass or ceramic bowl and add the lamb cutlets, turning to coat thoroughly. Cover with plastic film and leave to marinate in a cool place (not the fridge) for half an hour.
2. Cook cutlets on a preheated chargrill over medium–high heat for about 2 minutes on each side, turning a few times so the maple syrup doesn’t burn and blacken, until the lamb is medium-rare, or until done to your liking. Remove the cutlets to a bowl and rest, loosely covered, for about 5 minutes before serving.
3. Arrange the lettuce on a large serving platter and scatter the tomatoes and onion over the top. Drizzle the oil over the salad and put the lamb cutlets on top, spooning over any remaining juices from the resting process and adding a generous sprinkle of salt.