Slow Cooker Pulled Pork

Combine onion, ketchup, tomato paste, apple cider vinegar and spices in the bowl of a slow cooker. Season pork shoulder all over with salt and pepper then add to slow cooker, covering it with ketchup mixture. Cover and cook until very tender (the meat should fall apart easily with a fork!), on HIGH for 5 to 6 hours or on LOW for 8 to 10 hours.  Remove pork from slow cooker and transfer to bowl. Shred with two forks and toss with juices from the slow cooker. Serve on buns with coleslaw.