Cook the rigatoni in heavily salted water until just shy of al dente. Reserve about ¾ cup pasta water, then drain.
Heat the olive oil in a large skillet over medium-low heat. Add the garlic and cook for about 30 seconds.
Add the Calabrian chili paste and tomato paste. Cook for 4–5 minutes, stirring frequently, until the tomato paste darkens slightly and begins sticking to the pan.
Lower the heat and slowly stir in the heavy cream. Add the butter, salt, pepper and optional sugar. Simmer gently for 2–3 minutes.
Add the rigatoni and ½ cup pasta water. Toss over medium-low heat until the sauce becomes glossy and coats the pasta. Add more pasta water if needed.
Turn off the heat and stir in the Parmesan. Taste and add more chili paste or salt as desired.
Serve immediately with extra Parmesan.