In a large skillet, begin browning the Italian sausage over medium heat. After about 3–4 minutes, add the chopped onion and continue cooking until the sausage is fully browned and the onions are soft. Reduce the heat to low, then add the garlic, marjoram, black pepper, rosemary, thyme, and crushed red pepper. Cook for about 1 minute, stirring constantly to release the fragrant aromas. Remove the sausage mixture to a plate and cover with foil.

Meanwhile, cook the rigatoni according to the package instructions until al dente. Drain well and set aside.

Pour the chicken broth into the skillet, scraping the bottom with a wooden spoon to deglaze and capture all those flavorful brown bits left behind by the sausage. Stir in the heavy cream and bring to a boil. Once boiling, reduce the heat and let it simmer until the mixture reduces by about half. This step can take 15–20 minutes, so be patient—it’s what gives the sauce its luscious, velvety consistency.

Once reduced, turn the heat to low and stir in the Parmesan cheese, sundried tomatoes, and spinach. Stir gently until the cheese melts and the spinach wilts.

Return the sausage mixture to the skillet, then add the cooked pasta. Toss everything together until the rigatoni is evenly coated in the creamy sauce. Taste and adjust with salt and pepper as needed. Continue cooking over low heat until everything is heated through.

Serve hot, topped with extra Parmesan if desired.