Stuffed Cabbage Soup

Name: Stuffed Cabbage Soup
Ingredients: 1 1/2 pounds ground beef; 1 medium yellow onion, chopped; 3 cloves garlic, minced; 1 1/4 pounds cabbage, shredded; 1/2 cup sauerkraut, rinsed in cold water and squeezed dry; 2 1/2 quarts beef stock; 14 1/2 ounces canned diced tomatoes; 1/2 cup conventional white rice; salt and pepper; 2 tablespoons corn starch (optional); sour cream (optional); 1/2 cup lemon juice