1/2 cup red wine
3 tablespoons sugar
In a non-reactive skillet, cook the red wine and sugar until the bubbles get thick (see photo above.) Once the syrup is reduced to half its original quantity, remove from heat and scrape into a bowl to cool completely.
From David Lebovitz:
You could add a speck of cinnamon, black pepper or some seeds from a vanilla bean to this reduction. Just remember that it’s going to cook down, so add a very small amount at the beginning, if you do. This is also a good way to use up leftover poaching liquid from fruit.