In a large pot, blanch the veal intestines in boiling water for 5 minutes to remove any impurities.
Drain and rinse the intestines and cut them into small pieces.
In a large skillet, sauté the onion and garlic in olive oil until translucent.
Add the veal intestines to the skillet and cook over medium heat for 10 minutes, stirring occasionally.
Add the canned tomatoes and red wine to the skillet and let the sauce simmer for 2 hours, or until the veal intestines are tender and the sauce has thickened.
Season the sauce with red pepper flakes, salt, and pepper to taste.
Cook the rigatoni in a large pot of salted boiling water according to package instructions until al dente.
Drain the pasta and add it to the skillet with the tomato sauce and veal intestines.
Toss the pasta with the sauce to combine.
Serve the rigatoni alla pajata hot, topped with grated Pecorino Romano cheese.