Mix the tomatoes with all the other ingredients up to and including the salt, puree.
Make diamond-shaped incisions (approx. 2 cm deep) in one side of the medallions. Heat the clarified butter in a frying pan. Reduce the heat, fry the underside of the meat for approx. 4 mins., remove and season. Coat the raw side with the tartare sauce, sprinkle with parsley, leave to rest for approx. 5 mins.