Coat a rimmed roasting pan with nonstick cooking spray.
In a small bowl combine pepper, garlic powder and onion powder. Rub pepper mixture over pork. Place pork in pan.
Roast 25 – 30 minutes or until an instant-read thermometer registers 145°F, or to desired doneness. Remove pork from oven and let stand 10 minutes.
Meanwhile, for the sauce, in a small nonstick saucepan heat oil over medium heat. Add shallots and cook 3 – 5 minutes, or until softened. Stir in vinegar and mirin. Bring to a boil. Reduce heat and simmer 10 – 15 minutes or until slightly thickened.
Slice pork and transfer to a serving platter. Spoon sauce over pork and serve.