Jellied Cranberry and Port Sauce

In a large saucepan combine the cranberries, the sugar, the Port, the zest, and the lemon juice, simmer the mixture, stirring occasionally, for 15 to 20 minutes, or until the berries have burst and the mixture has thickened, and let it cool. Spoon the mixture into a lightly oiled 1-quart decorative mold and chill it, covered, for at least 3 hours or overnight. Run a thin knife around the edge of the mold, dip the mold into warm water for 10 seconds, and invert it onto a servi