Bring a large pot of salted water to a boil. Add the rigatoni and cook until al dente, about 8-10 minutes. Drain, reserving ½ cup pasta water.

In a large skillet, heat olive oil over medium-high heat. Add the sausage, breaking it apart. Cook until browned and fully cooked, about 5-7 minutes.

Push the sausage to one side and add the diced onion, sautéing until translucent, about 4 minutes. Add the minced garlic and cook for another 30 seconds.

Stir in the tomato paste and cook for 1 minute, blending with the sausage and aromatics.

Pour in the heavy cream and stir until combined. Simmer gently for 5 minutes to thicken.

Add the cooked rigatoni to the skillet, tossing to coat in the creamy sauce. If too thick, add reserved pasta water and simmer for 2-3 minutes.

Turn off the heat, stir in Parmesan cheese, sprinkle with parsley, season, and serve hot.