How to Make It
In a medium saucepan, cook the pancetta over moderate heat until browned and crisp, about 6 minutes. Add the onion, marjoram and crushed red pepper and cook until the onion is softened, about 8 minutes. Add the carrot and tomatoes, season with salt and simmer over moderately low heat, stirring occasionally, until the sauce has thickened, about 40 minutes.
Meanwhile in a large pot of salted boiling water, cook the bucatini until al dente. Drain and transfer back to the pot. Stir the butter into the tomato sauce and add to the bucatini. Toss to coat, season with salt and serve.