Heat the olive oil in a large, deep skillet or Dutch oven over medium-high heat. Add the sausage and cook for 5–7 minutes, breaking it into small pieces, until browned and fully cooked; drain excess fat if necessary.

Add the diced onion and cook for 3–4 minutes, stirring occasionally, until softened. Stir in the garlic, Italian seasoning, and optional red pepper flakes, then cook for about 30 seconds until fragrant.

Sprinkle the flour over the sausage and aromatics, stirring for 1 minute so it coats everything evenly. Gradually whisk in the chicken broth, scraping up the browned bits from the bottom of the pan.

Pour in the heavy cream and bring the mixture to a gentle simmer. Add the refrigerated tortellini and sliced sun-dried tomatoes, cover loosely, and simmer according to the package directions, usually 5–8 minutes, until the tortellini is tender.

Stir occasionally while the tortellini cooks so it does not stick and the sauce remains evenly mixed. Keep the heat gentle rather than allowing the cream sauce to boil aggressively.

Add the baby spinach and cook for 1–2 minutes, stirring until the leaves wilt into the sauce. Remove the skillet from the heat, stir in the Parmesan, and season with kosher salt and black pepper.

Garnish with chopped fresh basil or parsley and additional Parmesan if desired. Serve immediately while the tortellini is tender and the sauce is warm and creamy.