Heat a tablespoon of oil in a heavy pan. Strip the rosemary needles from the branch and then chop finely. Put the Robusta oil and rosemary needles in a mold and put the mold in the oven.
Sear the steak in the pan on both sides and then place in the preheated dish. Turn once to start. Leave in the oven at 80 degrees for approx. 30 minutes (medium).