1. Heat a large Dutch oven or soup pot over medium-high heat. Add the Italian sausage and cook, breaking it up with a spoon, until browned. Drain excess grease if needed.

2. If needed, add a bit of olive oil, then add diced onion. Sauté until translucent. Add minced garlic and tomato paste; cook for 30 seconds.

3. Pour in chicken broth and water. Add diced tomatoes, Italian seasoning, red pepper flakes, salt, and pepper. Stir and bring to a boil.

4. Reduce heat and simmer the soup for 10–15 minutes to blend flavors.

5. Add tortellini and simmer according to package instructions (usually 5–7 minutes).

6. Stir in spinach and cook just until wilted (1–2 minutes).

7. Serve hot with parsley and grated Parmesan if desired.