01 - Pat the brisket dry with paper towels. In a small bowl, combine smoked paprika, brown sugar, garlic powder, onion powder, black pepper, salt, cayenne pepper, and dried thyme. Rub the spice mixture thoroughly over all surfaces of the beef.
02 - Arrange the sliced onion and minced garlic evenly across the bottom of the slow cooker. Place the seasoned brisket on top of the aromatics, positioning the fat side facing upward.
03 - In a separate bowl, whisk together tomato ketchup, apple cider vinegar, brown sugar, Worcestershire sauce, Dijon mustard, smoked paprika, garlic powder, onion powder, salt, black pepper, and beef broth until smooth. Pour half of the sauce over the brisket; reserve the remaining sauce for serving.
04 - Cover the slow cooker with its lid. Cook on low heat setting for 8 hours, or until the brisket is fork-tender and easily shreds with gentle pressure.
05 - Carefully remove the brisket from the slow cooker and transfer to a cutting board. Allow the meat to rest for 10 minutes to redistribute juices. Slice the brisket against the grain into thin strips for maximum tenderness.
06 - Skim excess fat from the cooking juices remaining in the slow cooker. Serve the sliced brisket with the reserved BBQ sauce, warmed if desired. The remaining cooking liquid can be reduced and served as an additional au jus.