Heat a large pot over medium heat. Add the sausage and cook until browned, breaking it into crumbles as it cooks.
Add the diced onion and sauté until softened, about 5 minutes. Stir in the garlic and cook for another minute.
Pour in the chicken broth, heavy cream, diced tomatoes, Italian seasoning, and red pepper flakes. Bring to a gentle simmer.
Add the cheese tortellini and cook according to package instructions, usually 7-9 minutes.
Stir in the fresh spinach and allow it to wilt. Season with salt and pepper to taste.
Serve hot and enjoy!