In a large saucepan, cook the rigatoni until al dente. Drain the pasta, reserve 1 cup of the cooking water.

In a large saucepan, heat the olive oil. Add the bacon and onion and cook over moderately high heat, stirring occasionally, until the onion is softened and the bacon is browned, 5-7 minutes. Add the tomato paste and crushed red pepper and cook, stirring, for 1 minute. Stir in the strained tomatoes and bring the sauce to a simmer.

Add the pasta and reserved cooking water to the sauce and cook over moderate heat, tossing, until the pasta is coated. Remove from the heat and stir in the 1/2 cup of cheese and parsley. Season the pasta with salt and black pepper and transfer to bowls. Garnish with more chopped parsley.