HOW TO PREPARE IT:

Put a pan full of water on the fire and bring to the boil.
In the meanwhile prepare the dressing. Put a frying pan on the fire, add the oil and the chopped onion.
Let it fry gently for a few minutes and stir frequently.
Add the tomato sauce with truffle, a few tablespoons of cooking water and leave on the fire for a few more minutes and turn it off.
Cook the egg tagliatelle in salted water and drain them two minutes before the expected cooking time expressed on the package.
Pour the tagliatelle in the pan of the condiment, add the Parmigiano Reggiano cheese and mix over a low heat for a few minutes.