If you are using fresh tomatoes, slice them in half and with your hands press out the seeds and liquid through a sieve set over a small bowl. Chop the flesh into 1/2-inch pieces. Press the seeds and liquid through the strainer to retrieve the tomato juices and reserve them for later. In a 4-quart saucepan, heat the oil. When hot, add the onion and cook for 5 minutes or until golden. Add the pancetta or bacon and cook for 2 to 3 minutes. Add the crushed red pepper and white wine and boil, over high heat, until half the liquid remains. Add the tomatoes and reserved juices and simmer for 15 minutes over low heat or until the oil separates from the tomato juice. Season lightly with salt and add more crushed red pepper if you wish. While the sauce is cooking, bring a gallon of salted water to a boil. Add the bucatini pasta and cook for 10 minutes or until "al dente" (cooked through but still firm to the tooth). Right before draining, remove 1/4 cup of cooking water and reserve.Drain the bucatini and immediately add it to the sauce pot, off the heat, toss it with the sauce and the reserved cooking water. Add the cheeses and toss thoroughly. Adjust the seasoning and serve immediately with more cheese on the side. Serve with additional grated cheese, if desired.