1using kitchen string, tie together parsley, carrot, celery and Bay leaf. Set aside bundle.
2In a wide heavy pan, heat oil over medium heat until hot but not smoking. Add onion and cook, stirring occasionally, five minutes. Do not Brown. Add parsley bundle, tomatoes and reserved 1/3 cup juices, and 1/2 teaspoons salt and generous pinch pepper.
3Using a wooden spoon, stir sauce and break up tomatoes. Bring to a very gentle simmer and cook, stirring occasionally, one hour. When sauce is about 20 minutes from being done, bring a large pot of salted water to a boil.
4Remove sauce from heat. Remove and discard parsley bundle. Cover sauce to keep warm.
Cook pasta in the boiling water until al dente. Drain and transfer to a large serving bowl. Add sauce, butter and cheese. Toss to combine well. Adjust seasoning to taste. Serve at once, sprinkled with extra cheese. Serves 4 to 6.