How to Make It
In a medium bowl, mix the onion with the ketchup, brown sugar, cider vinegar, molasses, mustard and sambal oelek. In a slow cooker, cover the pork with the ketchup mixture. Cook on high until the pork is very tender, about 6 hours. Transfer the pork to a work surface and, using 2 forks, shred the meat.
Pour the sauce into a large saucepan and bring to a boil. Cook over high heat until thickened, about 15 minutes. Stir the shredded pork into the sauce, season with salt and pepper and serve.