Bring a large pot of salted water to a boil. Cook pasta until al dente. Reserve 1 cup pasta water, then drain.
In a large skillet over medium-low heat, melt butter. Add garlic and sauté gently until fragrant, about 1–2 minutes.
Pour in heavy cream and bring to a gentle simmer. Cook for 2–3 minutes, stirring occasionally.
Reduce heat and gradually stir in Parmesan cheese until melted and smooth.
Add cooked pasta to the skillet and toss to coat evenly.
Add reserved pasta water a little at a time until the sauce reaches desired consistency.
Season with black pepper and salt if needed.
Serve immediately with extra Parmesan on top.