Heat a Dutch oven or large skillet over medium-high heat. Cook and stir beef and onion in the hot Dutch oven until browned and crumbly, 5 to 7 minutes; drain and discard grease. Add cabbage, tomatoes, tomato sauce, water, garlic, salt, and pepper and bring to a boil. Cover Dutch oven, reduce heat, and simmer until cabbage is tender, about 30 minutes.
