CLEAN THE duck, salt and pepper the inside, and truss the bird. Roast or pot-roast it in butter as you would a chicken . Roast it according to the size, 25 to 30 minutes for a very small bird, or up to 50 minutes for a 4- or 5-pound one. By the time the duck is done, have ready all the elements of the sauce that follows.

Pare off thinly the yellow peel or "zest" of one grapefruit, taking care not to include any of the white rind underneath, and mince it finely. In a small saucepan, combine the white wine, grapefruit peel, and 4 teaspoons of sugar, and heat over a moderate fire until the sugar dissolves.

Squeeze all the juice from one grapefruit, strain it, and reserve. Peel the second grapefruit completely, divide it into sections, remove the seeds, and carefully remove all white filaments. Arrange the sections in a small baking dish, sprinkle them with confectioners' sugar, and glaze them in a very hot oven; keep them warm.

In a small covered saucepan, heat the cherries in a few spoonfuls of the Port.

When the duck is done, transfer it to a heatproof dish and place it over low heat. Pour all the fat out of the roasting pan and discard it. Pour the remaining Port into the roasting pan, place it over direct heat, and stir in the white-wine and grapefruit-peel mixture, the reserved grapefruit juice, the Port in which the cherries were warmed, the cherry syrup, and the MEAT JELLY, or substitute. Season lightly with salt and a pinch of paprika, and simmer the sauce until it is reduced and begins to thicken. At the very last, add the cherries.