Bring a large pot of water to a rolling boil and add 1/2 teaspoon kosher salt. Stir in the spaghetti and cook until al dente, about 8 to 10 minutes. Reserve 1 cup of pasta water, then drain.

Melt the butter in a large skillet over medium heat. Once it’s melted and foamy, add the garlic and red pepper flakes. Sauté until fragrant, about 1 to 2 minutes.

Add the drained pasta to the skillet along with Pecorino Romano, a splash of reserved pasta water, salt and pepper. Toss until the sauce is glossy and coats each strand, adding more water if needed.

Remove from heat, stir in olive oil and parsley, then serve immediately.