Rinse the tenderloin with cold water and dry with paper towels, then cut into three parts.
Heat a deep frying pan, melt the butter and quickly fry the tenderloin on all sides over high heat. It is not necessary to bring the meat to readiness yet, you just need to seal all the juices inside each piece.
Then turn down the heat, pour in the white port and maple syrup, salt the meat. Cover the pan with a lid and cook the meat over low heat until tender (about 20 minutes). About every 5 minutes, open the lid and pour the meat sauce formed at the bottom of the pan. You can not water each piece, but simply turn the tenderloin over, helping yourself with cooking tongs.