Bring a large pot of salted water to a boil. Add the pasta and cook as the label directs. Reserve 1/2 cup cooking water, then drain.
Meanwhile, combine the heavy cream and butter in a large skillet. Bring to a simmer over medium-high heat, whisking to combine. Whisk in the nutmeg and 1/2 teaspoon each salt and pepper. Keep warm over low heat.
Add the pasta and cheese to the sauce. Increase the heat to medium and toss to coat, adding the reserved cooking water as needed to loosen the sauce. Transfer the pasta to bowls and top with more parmesan.