Creating Spicy Sausage and Tortellini Soup is a simple process if you follow these comprehensive steps:

1. Brown the Sausage: In a large pot, heat the olive oil over medium heat. Add the spicy Italian sausage, breaking it apart with a spoon as it cooks. Cook until browned, about 5-7 minutes.

2. Sauté Onions and Garlic: Add the diced onion and minced garlic to the pot, stirring well. Cook for an additional 3-4 minutes until the onions become translucent.

3. Add Liquids: Pour in the chicken broth and diced tomatoes (including their juices). Stir to combine and bring to a gentle boil.

4. Add Tortellini: Once boiling, stir in the cheese tortellini and Italian seasoning. Allow it to cook for about 5-7 minutes, or until the tortellini are tender.

5. Incorporate Spinach: Stir in the fresh spinach and red pepper flakes, allowing the spinach to wilt for about 2-3 minutes.

6. Season: Taste the soup and adjust the flavor with salt and pepper, as needed.

7. Serve: Ladle the soup into bowls, garnishing with grated Parmesan cheese on top for added flavor.

These steps will guarantee a rich and delightful Spicy Sausage and Tortellini Soup that everyone will enjoy.