Allow brisket to sit out for about 30 minutes prior and preheat oven to 200F while you prepare the brisket with the rub.
Rub generously all over the brisket, covering all sides.
In a skillet over medium-high heat, melt butter (or use oil) sear the brisket for a few minutes on each side to get a nice crust.
Meanwhile, prepare a baking sheet in foil then transfer the brisket to it, fat side up, and pour any pan juices on top.
Cook for about 3 hours, or until the internal temperature reaches 165-170F and the exterior is dark and set. Wrap tightly in foil (pouring all pan juices back inside, place back in the oven on the baking sheet and increase the temperature to 275F.
Continue cooking until the tenderness is achieved. If you can insert an instant thermometer probe with ease in a few places, making sure you are mid-way between the bottom up to the start of the fat, not the top of the brisket, that is your center, there should be no resistance at all. You can start checking when you are about another 3 hours into the cook; about 6 hours in total.
Every brisket cooks a little differently, so pay attention to how it feels rather than focusing only on time or temperature. If the probe meets resistance in any area, keep cooking in 30-minute increments until it slides in smoothly.
Remove from the oven, leave wrapped and rest for at least 60 minutes, then slice across the grain.