Slice the tops of the peppers and keep the green top attached to the cap. Remove the seeds inside. With a small, sharp knife, carve little jack o' lantern on each pepper.
In a large bowl, combine beef, 1 cup cheese, tomatoes, rice, salt, pepper, garlic powder, and Italian seasonings. Stir until all ingredients are fully incorporated.
Stuff peppers with the beef mixture. Place them in a slow cooker, top side up. Cover and cook on high for 3 hours.
When the peppers are tender, top peppers with remaining cheese and cover. Cook on low for 5-10 minutes more, or until cheese melts.