Heat olive oil in a cast iron or heavy bottom skillet. Salt and pepper all sides of pork roast and sear in skillet. Remove and place in crock pot. Sear onions in hot pan until slightly browned. Place onions in crock pot with pork loin.
In a medium size bowl, mix apple cider, soy sauce, honey, brown sugar, garlic, salt and red pepper. Pour over roast. Place pineapple chunks around pork and cover with lid. Cook on HIGH for 5 hours or LOW for 7.
When done, remove pork and pineapple from slow cooker and place on serving platter. Turn slow cooker on high, add cornstarch slurry and stir to mix well. As mixture starts to bubble, keep stirring until desired thickness is achieved. Spoon gravy over pork loin. Serve!