Bring a large pot of generously salted water to a boil. While water heats, cut guanciale into thin strips and hand-crush the tomatoes in a bowl, discarding any hard cores.

In a large skillet over medium heat, cook the guanciale strips slowly, stirring occasionally, until fat renders and they turn golden and crispy, about 8–10 minutes. Remove guanciale with a slotted spoon and set aside, leaving the rendered fat in the pan.

If using wine, pour it into the hot skillet and scrape up any browned bits from the bottom. Let it bubble and reduce by half, about 2 minutes.

Pour the crushed tomatoes into the skillet and stir in the red pepper flakes. Bring to a gentle simmer and cook, stirring occasionally, until the sauce thickens slightly, about 15 minutes. Taste and adjust seasoning — it may need only a tiny pinch of salt because the guanciale and cheese are salty.

Meanwhile, cook bucatini in the boiling water according to package directions until al dente. Reserve about 1 cup of pasta cooking water, then drain the pasta well.

Add the drained bucatini to the simmering sauce along with half of the reserved guanciale and a splash of pasta water. Toss vigorously with tongs over medium heat for 1–2 minutes until the sauce clings to the pasta. Remove skillet from heat.

Sprinkle the grated pecorino over the pasta and toss again. Plate in warm bowls, top with the remaining crispy guanciale and extra pecorino. Serve immediately.