Place pork shoulder on top of onions, sprinkle with remaining dry rub (if there is any).
Cook on low for 8 hours or high for 4 hours.
Remove pork from slow cooker and shred with two forks.
Stir back into juices and add the BBQ sauce.
Serve pulled pork on buns with more sauce if desired.
For a gluten-free version, be sure to buy gluten-free buns or enjoy on a corn tortilla instead.
Freeze leftovers with juices in airtight containers or plastic bags for up to six months to use in carnitas tacos, more sandwiches, in tortilla soup, or just plain.
To make your own pork dry rub, mix together: 2 teaspoons each of garlic powder, oregano, paprika (smoked or regular), salt, pepper, and 1 teaspoon of cayenne pepper. Store any extra in your pantry in an airtight jar or container for future use.
The provided nutrition information does not include any added sodium from seasoning to taste, any optional ingredients, and it does not take brands into account. Feel free to calculate it yourself using this calculator or by adding the recipe to Yummly.