Cut the ham into large cubes, finely chop the onion. Fry in vegetable oil.
Add mashed tomatoes, salt and simmer over low heat for 3-5 minutes.
Add the grated cheese and stir quickly.
Boil the pasta in advance and discard in a colander.
Add the pasta to the sauce and stir. Warm up a little and remove from the stove.
Place on a serving platter and sprinkle with grated cheese to garnish. Sprinkle with finely chopped parsley before serving.