Chop enough reserved green pepper tops to equal 1/4 cup; set aside. Discard remaining tops or use for another purpose.

Place hollowed-out green peppers in a microwave-safe dish; cover and cook in microwave until bright green and steaming, about 3 minutes. Set peppers aside.

Cook and stir ground beef in a skillet with onion and 1/4 cup chopped pepper tops over medium heat until beef is browned, the juices run clear, and the onion is translucent, about 10 minutes. Drain excess grease.

Pour in diced tomatoes with their juice, rice, water, Worcestershire sauce, salt, and black pepper; bring to a boil. Reduce heat to low, cover skillet, and simmer until rice is tender, about 30 minutes.

Preheat the oven to 350 degrees F (175 degrees C).

Stir Cheddar cheese into ground beef-rice mixture and spoon mixture into precooked peppers. Set peppers upright in an 8x8-inch baking dish.