Spaghetti alla Gricia
Serves 6

• Kosher salt
• 1/4 cup extra virgin olive oil 
• 4 ounces sliced guanciale or pancetta, or good American bacon, cut into ½-inch-wide strips
• 1 medium red onion, halved lengthwise, ends trimmed, and cut lengthwise into ¼-inch-wide slices 
• 1 tablespoon coarsely ground black pepper 
• 1 pound spaghetti
• 1/2 cup freshly grated Parmigiano-Reggiano, plus extra for serving
• 1/2 cup grated pecorino romano 
• 1/3 cup coarsely chopped fresh Italian parsley

Bring 6 quarts of water to a boil in a large pot and add 3 tablespoons kosher salt.

Meanwhile, combine the oil, guanciale, and onion in another large pot and cook over medium-high heat, stirring frequently, until the guanciale is lightly browned and the onion is softened, about 7 minutes. Stir in the pepper and remove from the heat. 

Drop the pasta into the boiling water and cook until just al dente. Drain, reserving about ½ cup of the pasta water.

Add the pasta and ¼ cup of the reserved pasta water to the guanciale and stir and toss over medium heat until the pasta is well coated (add a splash or two more of the reserved pasta water if necessary to loosen the sauce). Stir in the cheeses and parsley and serve immediately, with addi¬tional grated Parmigiano on the side.