Salt and pepper
Dark brown sugar
Preheat the oven to 425 degrees and line a baking sheet with foil. Season the pork loin with salt and pepper and open roast the pork on a rack for 30 minutes.
Brush the entire surface of the roast with the Dijon, then press brown sugar into the mustard, all over the roast. Return the roast to the oven, reduce the heat to 375 degrees. Continue to roast until the internal temperature of the roast hits 145-150 degrees on a meat thermometer. Baste the roast in the drippings/sauce several times during the cooking time. Let the roast rest for 10 minutes before carving and serving.