Heat a cooking spray coated grill pan over medium-high heat.
Mix salt, basil, and pepper. Using half the mixture, season tomato and onion. Massage lamb with the other half.
Arrange tomato, onion, and lamb on grill pan. Grill tomato and onion 2 minutes per side and grill lamb 8 minutes per side or until preferred degree of doneness. Vegetables should be golden and tender; lamb should be browned and slightly pink in the center.