Season the beef liberally on all sides with salt and pepper. In a pan set to medium-high heat, add the butter and sage leaves. Once the butter melts, place the tenderloin in the pan and sear on one side for 2-3 minutes. Flip and sear other side for 2-3 minutes.
While cooking, baste the tenderloin regularly with the butter sage sauce.
Let the meat rest for 3-4 minutes, and sprinkle with salt and pepper.