01 - Preheat oven to 300°F.
02 - Mix salt, pepper, smoked paprika, garlic powder, onion powder, and brown sugar. Rub mixture all over the beef.
03 - Heat olive oil in a large Dutch oven over medium-high heat. Sear beef on all sides until browned, about 8 minutes total.
04 - Remove beef and set aside. Add chopped onions and garlic to the pot; sauté for 2-3 minutes until fragrant.
05 - Return beef to the pot. Pour in beef broth, barbecue sauce, Worcestershire sauce, and apple cider vinegar. Bring to a simmer.
06 - Cover and transfer to oven. Braise for 3 hours, or until beef is fork-tender.
07 - Remove beef and shred using two forks. Skim excess fat from braising liquid, then return shredded beef to the pot and toss to coat.
08 - Preheat oven to 350°F. Slice slider buns and brush with melted butter. Toast in oven for 5-7 minutes until lightly golden.
09 - Pile pulled beef onto bottom bun halves, top with pickle slices and red onion. Cover with top buns.
10 - Serve warm.