Brown the sausage: Heat a large pot or Dutch oven over medium-high. Add a drizzle of olive oil, then the sausage.
Break it up with a spoon and cook until browned and cooked through, about 6–8 minutes. Spoon off excess fat if needed.
Sauté the aromatics: Add onion, carrots, and celery. Cook, stirring, until softened, 5–6 minutes.
Stir in garlic and cook 30 seconds until fragrant.
Build the broth: Add crushed tomatoes, chicken broth, Italian seasoning, and red pepper flakes. Stir, scraping up any browned bits from the bottom of the pot for extra flavor.
Simmer: Bring to a gentle boil, then reduce heat and simmer 10 minutes to let the flavors meld and the vegetables finish softening.
Cook the tortellini: Add tortellini and simmer according to package directions, usually 3–5 minutes, until they float and are tender.
Add cream and greens: Lower the heat. Stir in the cream and spinach (or kale).
Cook 1–2 minutes, just until the greens wilt and the soup looks creamy.
Season and serve: Taste and add salt and black pepper as needed. Ladle into bowls and top with grated Parmesan and fresh herbs if you like.