Preheat oven to 400 degrees F. Drizzle the tenderloin with oil
. Season well with plenty of salt and pepper. Sprinkle with assorted fresh herbs. Allow the tenderloin to come to room temperature before cooking. Place a large cast-iron skillet
over medium-high heat and sear tenderloin on all sides (add additional oil, if necessary). Place the skillet in the preheated oven and roast the tenderloin for about 15 to 17 minutes. (At this point, a meat
thermometer inserted into the thickest part of the meat should read 135 degrees F for medium rare; for medium, roast for 3 minutes more.) Remove from the oven. Tent tenderloin with foil; allow to rest for 10 minutes before slicing. Serve with Blender
Bearnaise (see below). If you like, garnish with watercress.