In a small saucepan, mix together the orange juice, zest and sugar
Simmer the mixture over medium heat, while stirring occasionally, for 15 minutes, until the formation of a thick and syrupy sauce.
You can continue to reduce
the sauce to make it thicker, if you prefer.
Stir in the butter when the sauce is a consistency you’re looking for.
Simmer the sauce for another 2 or 3 minutes then remove from heat and set aside to cool.
The orange sauce could be served chilled, at room temperature or warm.