01 - Combine smoked paprika, brown sugar, kosher salt, black pepper, garlic powder, onion powder, and cayenne pepper in a small bowl. Mix thoroughly to distribute spices evenly.
02 - Pat the beef brisket completely dry with paper towels. Press the spice rub mixture firmly onto all surfaces of the meat, ensuring even coverage. Allow seasoning to adhere for 5 minutes.
03 - Position the seasoned brisket in the slow cooker with the fat cap facing upward. This allows fat to render down and baste the meat during cooking.
04 - Whisk together tomato ketchup, apple cider vinegar, brown sugar, Worcestershire sauce, Dijon mustard, smoked paprika, liquid smoke, garlic powder, and onion powder in a separate bowl until completely smooth and incorporated.
05 - Pour half of the BBQ sauce mixture over the brisket in the slow cooker. Cover with lid and cook on low setting for 8 hours until fork-tender. Reserve remaining sauce for serving.
06 - Remove cooked brisket to a cutting board. Let rest uncovered for 10 minutes to allow juices to redistribute. Slice against the grain into thin strips for maximum tenderness.
07 - Remove and discard any excess fat from the liquid remaining in the slow cooker. This rendered liquid can be used as an additional serving sauce.
08 - Arrange sliced brisket on a serving platter. Serve alongside reserved BBQ sauce for guests to add as desired.