INSTRUCTIONS
1. In a fry pan over medium heat, cook the guanciale in the olive oil, stirring often, until golden, about 10 minutes. Add the onion and sautee until tender and golden, about 5 minutes. Add the garlic and red pepper flakes and sautee until the garlic is golden, about 1 minute more.
2. Pass the chopped tomatoes through a food mill fitted with the medium disk or a medium-mesh sieve directly into the pan. Add a pinch of salt, bring to a simmer and cook uncovered, stirring occasionally, until the sauce has thickened, about 15 minutes.
3. Meanwhile, bring a large pot three-fourths full of water to a rolling boil and add the 2 Tbs. salt. Add the bucatini, stir well and cook, stirring occasionally, until al dente, according to the package instructions. Scoop out and reserve about 2 ladlefuls of the cooking water, then drain the pasta.
4. Return the pasta to the pot, add the sauce and stir and toss over low heat until well coated, adjusting the consistency with some of the cooking water if needed. Sprinkle with the 1/3 cup cheese and toss again. Transfer the pasta to a warmed serving bowl and serve immediately, passing additional cheese at the table.