Cabbage Soup with Sausage

Name: Cabbage Soup with Sausage
Prep time: 10 min
Cook time: 35 min
Total time: 45 min
Cuisine: American
Ingredients: 14 ounces smoked kielbasa sausage (sliced); 1/2 large head cabbage (shredded); 6 cups chicken broth; 1/2 yellow onion (diced); 14.5 ounce can diced tomatoes (lowest carb); 1 carrot (sliced); 1 rib celery (sliced); 3 cloves garlic; 1 tablespoon tomato paste; 1 tablespoon olive oil; 1 tablespoon butter; 1 teaspoon dried thyme; 1 teaspoon salt (divided); 1/4 teaspoon ground black pepper; Optional: pinch of red pepper flakes