Bring a large pot of salted water to a rolling boil. Add pasta and cook until just shy of al dente — usually 1 to 2 minutes less than the package suggests. Reserve 1 cup pasta water, then drain.

In a wide skillet over medium heat, heat olive oil. Add the onion and sauté until translucent and sweet-smelling, about 4 minutes.

Add the minced garlic and red pepper flakes. Stir for 30 to 45 seconds until the garlic is fragrant and golden — not browned.

Pour in the crushed tomatoes and a pinch of salt. Bring to a gentle simmer and let the sauce reduce and thicken for 8 to 10 minutes, stirring occasionally.

Stir in the cream and Parmesan. If the sauce is too thick, add reserved pasta water a splash at a time until you reach the desired consistency.

Add the drained pasta directly into the skillet and toss to coat. Finish with butter (if using), lemon zest, and torn basil leaves. Taste and adjust salt and pepper.

Serve immediately with extra cheese and a drizzle of olive oil.