Pick through the cranberries and discard any that are squishy. Place them in the work bowl of a food processor.
Zest the whole orange directly into the food processor. Cut away and discard the remaining orange peel and white pith, and then cut the sections free from membranes. Add the orange sections to the work bowl, but discard the remaining membranes. (If you’re feeling rushed—or want the roughage, as my grandmother called it–you can chop the whole peeled orange.)
Add the sugar to the cranberries, orange sections, and zest, and pulse until finely chopped. You want a fine chop, but take care not to purée the mixture. Remove to a bowl and stir in the optional pomegranate seeds and liqueur.
Cover and refrigerate for several hours, but ideally overnight, to allow the flavors to develop.