Preheat oven to 400F.

Mix the seasoning rub ingredients in a small bowl. Tie the pork loin with cooking twine.

Rub the pork loin with the seasoning mix. Place the pork in a large roasting pan. Arrange the onions and pineapple slices around the pork loin.

Pour the pineapple juice into the pan. Bake at 400 F for 40 minutes.

Cover the pork with aluminum foil and lower the oven temperature to 350F. Baste the pork loin with the juices. Bake for about 1 hour and 20 minutes, basting every 20 minutes.

Take out of the oven, add the butter and let the pork rest for about 10 minutes before cutting and serving.

Meanwhile make the sauce: Strain the pan juices into a small pot and cook over high heat for about 15 minutes.

Add the cream and corn starch. Let the sauce cook over medium heat until it starts to thicken.

Slice the roasted pork loin and serve with the pineapple sauce and baked pineapples and your choice of side dishes.