Mix the first onion, carrots, garlic, peppercorns, salt, and wine. Marinate the brisket in the marinade, in the roasting pan you will use, for 48 hours (in the refrigerator), turning once or twice.
Cook the remaining sliced onions and sugar in oil for about 30 minutes, until brown and tender. Cool these and reserve. Use half of the browned onions with the brisket from the start and half to add during the last hour of roasting.
After marinating the meat, remove most of the solids, add the tomatoes, chile, garlic, pepper, nutmeg, and half the reserved
onions. Cover the pan with several layers of foil, tightly sealed. Roast at 300°F. for 6 hours. Remove the foil
and add the remaining onions. Roast for an additional hour, uncovered.