Preheat your smoker to 225°F using oak or hickory wood for an authentic Texas flavor profile.
Trim the beef brisket of excess hard fat, leaving a consistent quarter-inch layer on the fat cap to keep the meat moist.
In a small bowl, mix the coarse sea salt, black pepper, and garlic powder until well combined.
Apply the spice rub generously to all sides of the brisket, pressing it into the meat to ensure it adheres.
Place the brisket in the smoker fat-side up and smoke until the internal temperature reaches 165°F.
Wrap the brisket tightly in peach butcher paper to preserve the crust while allowing the meat to breathe.
Return the wrapped brisket to the smoker and continue cooking until the internal temperature reaches 203°F and it feels tender.
Remove the brisket from the smoker and let it rest in a dry cooler or a warm oven for at least 1 hour.
While the meat rests, whisk the olive oil and apple cider vinegar together, then toss with the shredded cabbage and sliced red onion.
Slice the rested brisket against the grain into thin strips and serve 6 ounces with the fresh vinegar slaw and warmed black beans.