Zest all the oranges and then squeeze out the juice. Pour into a saucepan and reduce by two-thirds over medium–high heat. Remove from the heat. Strain out the zest and discard it. Set the infused juice aside.
Make a dry caramel with the sugar by heating a quarter of the sugar in a clean saucepan over medium heat. When the sugar has melted, add in another quarter and heat until it melts.