Peel, rinse and finely chop the onion, Rinse the loin, once dried chop in into chunks. Rinse the basil, dry it and break it up delicately.Blanch the tomatoes for a minute, once drained, deseeded and peeled, place them in a sift and let them drain a bit more for 15 minutes to allow them to give out all the cooking liquid.Sift them into a bowl. Heat a knob of butter and a dash of oil in a pan, add the onion and half of the basil, fry them until soft but not golden, then add the meat and brown for until evenly golden, tipping it over with a wooden spoon.Add the tomato passata, season with a pinch of salt and ground pepper. Cover and simmer for half an hour over a medium heat.Keep stirring and add water if necessary. Then boil the pasta in plenty of salted water.Drain it al dente mix it with the ragù and grated parmesan. Mix well, toss the pasta in a serving dish, sprinkle with basil and serve immediately.