Prehat the oven to 400°F. Heat the oil in a large oven-safe skillet over medium-high heat. Remove any silver skin (membrane from the meat.) Seasib the meat to taste. Sear the tenderloin on all sides. About 2 minutes on each side: Top, bottom, front, back.
Place a spring of rosemary on each tenderloin and place the skillet in the oven. You'll want an internal temperature of 145 to 150° F. This should take around 15 minutes, depending on the thickness of the tenderloin.
Remove from oven and loosely tent with aluminum foil for 10 minutes. Slice and serve
