Trim excess fat from roast. Finely chop rosemary and garlic together. Make about 10 small slits in the roast with a sharp knife and insert small amounts of the chopped rosemary and garlic in the slits.
Sprinkle roast with salt and pepper. Heat butter in the roasting pan and toss in the chopped onion. Place pork on top of onion and drizzle with olive oil.
Roast, uncovered, at 350 degrees for about 2 hours, (don’t over cook) or until a meat thermometer registers 170 F. Remove from oven and let the roast stand for about 15 minutes before slicing.
Amazing with garlic mashed potatoes and steamed broccoli.
