01 - Combine kosher salt, black pepper, smoked paprika, garlic powder, onion powder, cayenne pepper, and brown sugar in a small bowl. Rub the mixture evenly over the brisket.
02 - Whisk together ketchup, apple cider vinegar, brown sugar, Worcestershire sauce, Dijon mustard, smoked paprika, garlic powder, onion powder, black pepper, and salt until smooth.
03 - Place the seasoned brisket in the slow cooker. Pour half of the BBQ sauce over the meat, reserving the remainder for serving.
04 - Cover and cook on Low for 8 hours until the brisket is tender and shreds easily.
05 - Remove the brisket and let rest for 10 minutes before slicing or shredding as preferred.
06 - Remove excess fat from the remaining sauce in the slow cooker.
07 - Serve the brisket with reserved BBQ sauce and garnish with chopped parsley if desired.