Trim the fillet, removing all sinew, then fold the thinner tail end under and tie with butcher’s string. This will give the fillet a consistent shape to ensure even cooking throughout.
Grind all spices in a mortar and pestle.
Add remaining ingredients and pound to chunky consistency.
Rub a little over beef and seal on hot griddle or pan.
Transfer to oven tray and with remaining spice mix coat the beef.
Bake in a hot oven until just cooked medium–rare, approximately 25–30 minutes.