Put corned beef into a roasting pan with a tight fitting lid (use aluminum foil to cover pan under lid to seal better). Pour wine over and spread dried onion soup on top. Pat it down with your hand so it covers the meat well.
Roast the meat, covered, in a preheated 275 to 300 oven until it is fork-tender. This usually takes 2 to 3 hours or more, depending on size of the beef.
When the meat is tender, spread the brown sugar evenly over the meat, return it to the oven and cook it uncovered until the sugar melts.
If you remove the beef 30 minutes before ready to serve, it carves easier. Very sharp knife, very thin slices.