Brown the sausage: Heat olive oil in a large pot over medium-high heat.
Add turkey sausage and cook, breaking it into small pieces, until browned and cooked through, about 5–7 minutes. Spoon off excess fat if needed.
Sauté aromatics: Add onion and cook until translucent, 3–4 minutes. Stir in garlic, Italian seasoning, red pepper flakes, salt, and black pepper.
Cook 30–60 seconds until fragrant.
Build the base: Stir in tomato paste and cook for 1 minute to caramelize slightly. Add diced tomatoes with their juices and chicken broth. Bring to a gentle boil.
Add beans and simmer: Stir in cannellini beans.
Reduce heat and simmer 8–10 minutes to let flavors meld.
Cook the tortellini: Add tortellini and simmer according to package directions, usually 3–5 minutes, until just tender. Do not overcook.
Finish with greens and cream: Stir in spinach (or kale) and cook until wilted, 1–2 minutes. Lower the heat and add half-and-half and Parmesan. Stir gently and heat through without boiling.
Brighten and taste: Squeeze in lemon juice.
Taste and adjust seasoning with more salt, pepper, or red pepper flakes as needed.
Serve: Ladle into bowls and top with extra Parmesan and fresh herbs, if using. Enjoy warm.