In a large skillet cook burger and onion until burger is no longer pink inside; drain if needed. Place the burger mixture in the bottom of the slow cooker and mix in the cabbage, green pepper, and rice.
In a large bowl mix together the water and tomato paste, and the mix in the rest of the ingredients. Add the mixture to the slow cooker and mix until well combined.
Cook on low for 4-5 hours or until rice and vegetables are tender.