Pat the beef brisket dry with paper towels and trim any excessively thick or hard fat, leaving a thin, even layer for flavor and moisture.

In a small bowl, combine kosher salt, freshly ground black pepper, smoked paprika, garlic powder, onion powder, brown sugar, ground cumin, chili powder, and cayenne pepper, stirring until evenly mixed into a dry rub.

Brush the brisket all over with olive oil, then generously coat it with the dry rub, pressing the mixture into the meat on all sides.

Let the seasoned brisket rest at room temperature for about 30 minutes to allow the rub to begin penetrating the meat.

Preheat your smoker or oven to 275°F (135°C). If using a smoker, prepare it for indirect heat according to the manufacturer’s instructions.

Place the brisket fat-side up in the smoker or in a roasting pan if using an oven, then pour the beef broth into the bottom of the smoker drip tray or roasting pan to create a moist cooking environment.

Cook the brisket at 275°F (135°C) for about 4 to 5 hours, or until the internal temperature reaches approximately 165°F (74°C), checking occasionally and adding more beef broth to the pan if it begins to dry out.

In a small bowl, stir together the barbecue sauce and apple cider vinegar until smooth to create a tangy glaze.

When the brisket reaches about 165°F (74°C), brush a layer of the barbecue sauce mixture over the top and sides of the meat, then cover the brisket tightly with foil if using an oven, or wrap it well in foil if using a smoker.

Return the wrapped brisket to the smoker or oven and continue cooking at 275°F (135°C) for another 2 to 3 hours, or until the internal temperature reaches 200–205°F (93–96°C) and the meat feels very tender when probed.

Remove the brisket from the heat source and let it rest, still wrapped, for at least 30 to 45 minutes so the juices can redistribute throughout the meat.

Unwrap the brisket, brush with a little more of the remaining barbecue sauce mixture if desired, then slice the meat against the grain into thin slices and serve warm with any collected juices spooned over the top.