Remove the corned beef brisket from the packaging and rinse well.
Dry the beef with paper towel and place in a roasting pan fat side up. Season the entire brisket with the seasoning packet, garlic powder, and onion powder.
Cover the roasting pan with foil and bake for 6 hours, or until the internal temperature is 200℉.
After baking for 4 hours, remove the foil to allow the exterior of the brisket to develop a crispy crust. Baste with the pan juices about every 30 minutes in the final hour to prevent the brisket from drying.
Once the corned beef has reached 200℉, remove from the oven, cover with foil, and allow to rest for 30-45 minutes before slicing.