Put on pasta water. Dab the beef fillet and cut into finger-thick strips. Cut the mushrooms into slices and the onion into small cubes. Briefly sear the meat in a pan (large), season with pepper and salt, remove it from the pan and set aside (it will cook again later).
Put the pasta in the boiling water. Fry the onions in the now empty pan until translucent. Add the mushrooms. Deglaze with red wine and dissolve the gravy cube in it. Add a dash of cream.
Drain the tomatoes and add them to the sauce. You can also use skinned, fresh tomatoes instead of canned tomatoes. Put the meat in the sauce. There is still a bit of a drag here (medium). Drain the pasta and add. Stir vigorously and serve.