Preheat the oven to 375 degrees F. Place the halved quinces, cut side down, in an ovenproof glass that is just large enough to contain them. Pierce each quince half with 2 or 3 cloves.
In a bowl, mix the wine, liqueur, sugar, and cinnamon. Stir and pour over the quinces. Bake for about 1 1/2 hours, basting frequently with the juices. Let quinces cool, then serve topped with yogurt and a teaspoon of quince spoon sweet , if you like.
