Bring a large pot of salted water to boil and cook rigatoni according to package directions until al dente. Reserve 1/2 cup pasta water before draining.

While pasta cooks, heat a large skillet over medium-high heat. Add sausage, breaking it into bite-sized chunks with a wooden spoon. Cook for 6-8 minutes until beautifully browned and cooked through.

Add diced onion to the same skillet with the sausage drippings. Cook for 3-4 minutes until softened and translucent. Stir in minced garlic and cook for another 30 seconds until fragrant.

Pour in crushed tomatoes, Italian seasoning, and red pepper flakes if using. Bring to a gentle simmer and let it bubble for 5 minutes, allowing flavors to meld.

Reduce heat to low and stir in heavy cream, creating a pink sauce. Add Parmesan cheese and toss in the drained pasta. If the sauce seems thick, splash in reserved pasta water until it coats each rigatoni tube perfectly. Season with salt, pepper, and fresh basil.