The tournedos come from the fillet of beef, one of the most tender cuts of beef, as do the fillet mignon and Chateaubriand. These are small steaks cut from the center, round and about 1 1/2 to 2 inches thick.
This is a classic way to prepare white flat fish, dredged in flour, cooked in butter, served with a brown butter sauce with lemon and parsley. Simple and flavorful.