Pat the beef brisket dry with paper towels and place it on a large cutting board.

In a small bowl, combine the kosher salt, black pepper, smoked paprika, garlic powder, onion powder, and ground cumin.

Rub the spice mixture evenly all over the brisket, pressing it gently into the meat on all sides.

Heat the olive oil in a large, heavy oven-safe pot or Dutch oven over medium-high heat.

Sear the brisket for 3 to 4 minutes per side, until nicely browned on all sides, then transfer it to a plate.

Reduce the heat to medium and in the same pot whisk together the ketchup, apple cider vinegar, brown sugar, Worcestershire sauce, Dijon mustard, beef broth, and liquid smoke (if using).

Bring the barbecue sauce mixture to a gentle simmer, stirring until the brown sugar has dissolved and the sauce is smooth.

Return the seared brisket to the pot, nestling it into the sauce and spooning some sauce over the top.

Cover the pot with a tight-fitting lid, reduce the heat to low, and let the brisket simmer gently for 3 1/2 to 4 hours, turning it once or twice, until the meat is very tender when pierced with a fork.

Transfer the cooked brisket to a cutting board and let it rest for 15 minutes, loosely covered with foil.

While the brisket rests, simmer the remaining barbecue sauce in the pot over medium heat for 5 to 10 minutes to slightly thicken, stirring occasionally.

Slice the brisket against the grain into thin slices and return the slices to the pot, turning them gently in the warm barbecue sauce.

Serve the tender brisket with homemade barbecue sauce spooned generously over the top.