Cook the pasta in salted water until al dente. Reserve a cup of pasta water, then drain. Pro move: don’t rinse.
In a large skillet, melt butter over medium heat. Add garlic and sauté for about 30 seconds until fragrant—not brown, just aromatic.
Pour in the heavy cream. Bring to a gentle simmer and let it thicken slightly, about 2–3 minutes.
Whisk in the lemon zest, lemon juice, and grated cheese. Stir until the sauce is smooth and glossy. If it’s too thick, splash in a bit of the reserved pasta water.
Season with salt, pepper, and red pepper flakes if you’re using them. Taste and adjust brightness with a touch more lemon if needed.
Add the drained pasta to the sauce. Toss to coat evenly, adding more pasta water as needed to reach a silky, clingy consistency.
Garnish with parsley or basil. Serve hot and revel in the citrusy creaminess.