Easy Taco Skillet

Heat a large skillet over medium heat; cook and stir beef and onion until beef is browned, about 5 minutes. Drain. Stir tomatoes, water, rice, and taco seasoning into beef mixture and bring to a boil. Reduce heat to medium-low, cover, and simmer until rice is tender, about 25 minutes. Top with Mexican cheese blend and lettuce before serving.