In a large bowl, mix meat, rice, salt, pepper and onion. In a lined crock pot, layer 1/3 cabbage, 1/3 sauerkraut(I use a large can because we love sauerkraut) 1/2 of the meat, 1/3 cabbage, 1/3 sauerkraut and the rest of the meat mixture. Last layer, top with remaining sauerkraut and cabbage. Mix soup with one can of water, pour over casserole (sprinkle with 2 tablespoons of brown sugar), cover and let stand for 30 minutes.Cook on low for 8 hours (without stirring). So delicious!