01 - Cook the pasta in a large pot of salted boiling water according to package instructions until al dente. Reserve 1/2 cup of pasta water, then drain.
02 - Meanwhile, heat olive oil in a large skillet over medium heat. Add the onion and sauté for 3–4 minutes until soft and translucent.
03 - Stir in the garlic and cook for 30 seconds, until fragrant.
04 - Add the crushed tomatoes, sugar, salt, black pepper, and red pepper flakes (if using). Simmer for 8–10 minutes, stirring occasionally, until slightly thickened.
05 - Reduce the heat to low. Stir in the heavy cream and grated Parmesan. Cook for 2–3 minutes, stirring, until the sauce is creamy and well combined.
06 - Add the drained pasta to the sauce and toss to coat, adding reserved pasta water a little at a time if needed to loosen the sauce.
07 - Remove from heat. Stir in fresh basil leaves.
08 - Serve immediately, topped with extra Parmesan and a sprinkle of fresh basil.