Step 1
In a bowl, combine onion, ketchup, vinegar, tomato paste, garlic powder, cumin, mustard powder, and paprika. Season pork shoulder all over with salt and pepper. Add to slow cooker, covering with ketchup mixture.
Step 2
Cover and cook on high 5 to 6 hours or on low 8 to 10 hours, until very tender (the meat should fall apart easily with a fork).
Step 3
Transfer pork to a large bowl. Shred with 2 forks and toss with juices from slow cooker. Serve on buns with coleslaw (if using).
