Toss together pork, onion, Rancher Rub and 1/4 cup Agave BBQ Sauce.
Transfer mixture to a slow cooker along with water. Place potatoes around pork roast and cook on low for 6 hours or high for 4 hours, until potatoes are cooked through and pork is very tender.
Remove potatoes from slow cooker and slice in half lengthwise without cutting all the way through. Use a fork to fluff the potato flesh.
Shred pork with forks or tongs. Toss with remaining 1/2 cup Agave BBQ Sauce.
Stuff potatoes with shredded pork. Top with shredded cheese and red onion. Broil to melt cheese if desired.
Serve with optional toppings such as sour cream and scallions.
