Remove the brisket from the package and discard the included spice pack.
Place the brisket in a pot of water and bring to a boil, then immediately remove to reduce excess salt.
Preheat the oven to 350°F.
Place the brisket fat side up in the center of a large piece of aluminum foil.
Rub the brisket evenly with Dijon mustard and sprinkle brown sugar over the top and sides, patting gently to adhere.
Loosely cover the brisket with the foil, leaving some space between the meat and foil, then set it in a rimmed roasting pan.
Bake the brisket for 2 hours, adjusting time if the brisket is larger, approximately 45-60 minutes per pound.
After baking, open the foil and broil on low or place on a lower oven rack to caramelize the topping, watching closely to prevent burning.
Remove the brisket from the oven and let rest for 10-15 minutes before slicing against the grain.