Step 2

In a medium skillet, melt the butter over medium heat. Add the guanciale and cook until the fat is fully rendered and the meat is well browned and crisp, about 5 minutes. Remove the meat from the pan with a slotted spoon and reserve.

Step 3

Add the onion to the pan and sweat until translucent, about 5 minutes. Stir in the chili paste and red-pepper flakes, season lightly with salt and generously with black pepper, and cook for about 1 minute, stirring constantly.

Step 4

Add the garlic and cook until fragrant, about 1 minute, then stir in the tomatoes and oregano. Reduce the heat to low and simmer, stirring occasionally, until the sauce thickens slightly, 15 to 20 minutes. Remove and discard the sprigs of oregano.

Step 5

While the sauce simmers, bring a large pot of salted water to a boil over medium heat. Add the bucatini and cook until al dente, according to package directions. Reserve ⅓ cup pasta water, then drain the pasta.

Step 6

Toss the pasta with the thickened tomato sauce over low heat. Add the reserved pasta water and the Pecorino Romano, and toss generously until the mixture is well combined and the sauce clings to the pasta. Add the reserved guanciale and toss to combine. Garnish with more cheese to serve.