Directions

1. To make the marinade, whisk together the liquid smoke, steak sauce, salt, pepper, and garlic powder in a bowl.
2. Line a roasting pan with aluminum foil. Place brisket with the fattier-side facing upwards in the center of the pan. Pour half of the marinade over the brisket. Using a food injector, inject the rest of the marinade into the brisket. Seal the brisket in the foil and refrigerate for at least 16 hours.
3. Preheat oven to 250 degrees F (120 degrees C). Open foil and layer onion slices on the brisket. Reseal the foil.
4. Bake in preheated oven for 6 hours. Remove the brisket and slice. Reseal the foil and bake the sliced brisket for 1 hour more.