Combine the steak pieces, tomato puree, seasonings, peppers, and onions in the slow cooker. Give everything a good stir with a wooden spoon.
Cover and cook on Low for 6-8 hours, or High for 3-4 hours.
45 mins before serving: Wash the rice, then add it and the beef stock to the slow cooker. Give it a good stir and cook on High for 45 mins.
Once finished, add the cheese and cover with a lid until the cheese is melted.
