Bring a pot of salted water to a boil and add in the bucatini. Cook the pasta just until al dente or a minute less. Reserve 2 cups of the pasta water before draining the pasta.

Heat a large skillet over medium heat. Add in the butter and when it's melted add in the garlic. Sauté just until the garlic is fragrant and then add in the pumpkin purée, black pepper, nutmeg, and a pinch of salt. Whisk until incorporated and then slowly pour in the pasta water, whisking until the sauce is smooth.

Add the pasta into the skillet and toss to coat it in the sauce. Add in the cheese and continue to toss the pasta until the cheese is melted into the sauce. If your sauce looks too thick, pour in additional pasta water and toss until incorporated.

Taste for seasoning and add additional salt and pepper if needed. Serve the pasta topped with Parmesan or Pecorino shavings if desired.