In the base of a 5 to 6 quart slow cooker, combine the chopped cabbage, water, uncooked rice, ground black pepper, garlic salt, paprika, sugar, the entire can of tomato sauce, and the can of diced tomatoes with all their juice. Add the browned ground beef mixture to the slow cooker as well. Using a large spoon, stir everything together thoroughly until all the ingredients are evenly combined and the cabbage and rice are well distributed throughout the tomato-based liquid. Make sure the rice is submerged in the liquid so it cooks properly.
Step 3: Cook Low and Slow
Place the lid on the slow cooker and cook on LOW for 4 to 5 hours, or on HIGH for 3 to 4 hours, until the cabbage is completely tender and the rice is fully cooked through. The timing can vary slightly depending on the age and model of your particular slow cooker — some run hotter than others, particularly newer models which tend to run at higher temperatures than older ones. Check for doneness during the last hour of cooking by tasting a piece of cabbage and a few grains of rice. Both should be completely tender before serving. Give the entire pot a thorough stir before ladling into bowls.
