Mix the arrowroot with 2 tablespoons of the red wine until smooth; set aside.
Put the remaining wine in a deep saucepan with the brown sugar, cinnamon stick, cloves, lemon zest, and orange zest. Warm gently, stirring until the sugar dissolves.
Peel the pears carefully, leaving the stalks attached. A potato peeler will allow for a less waste of the pear flesh than a paring knife. Your choice.
Place the pears in the wine mixture, cover, and poach at a gentle simmer for about 20 minutes, or until tender but still holding their shape. Turn carefully during cooking if needed for even color.
Lift the pears out with a slotted spoon and place them in a deep serving dish or individual dishes.
Strain the poaching wine through a fine-mesh sieve, discarding the cinnamon, cloves, and citrus zest.
Return the wine to the saucepan. Stir the arrowroot mixture again, add it to the wine, and cook over low heat while stirring until lightly thickened.
Pour the sauce over the pears and allow them to cool. Serve as they are or with fresh cream or crème fraîche.
Notes
Choose ripe-but-firm pears so they become tender without collapsing.
Comice pears are excellent; Bosc, Bartlett, Concorde, or Asian pears are suitable alternatives.
Arrowroot gives the clearest sauce and has little flavor. Cornstarch works if arrowroot is unavailable.
Poaching time varies with pear size, variety, and ripeness. Test the thickest part with a small knife.
This recipe contains alcohol. Cooking does not reliably remove all of it.
The pears may be prepared ahead and refrigerated in their sauce once completely cool.