Preheat the oven to 325F. Put a grate (roasting rack) in the bottom of a roasting pan or baking dish large enough to hold the meat.
Rinse the corned beef to remove packing. Pat it dry with a paper towel.
Trim the fat cap and place meat fat side up on roasting rack. Fill the bottom of the pan with enough water to reach the rack. Be careful NOT to submerge the meat in the liquid.
Cover the pan with a lid or aluminum foil. Bake the meat covered for 2 hours. Remove the lid and roast for an additional 1 hour or until an internal temperature of 185F is reached.
Remove from the oven and allow meat to rest for 15-20 minutes. Slice and serve.