1. Combine water and sugar over medium-high heat. Stir until sugar is dissolved, then bring to a boil without stirring.
2. Add all other ingredients except zest. Stir to mix, then bring to a simmer. Lower heat slightly and cook about 5 minutes, until mixture is thickened.
3. Remove from heat and add orange zest. Remove cinnamon stick.
4. Cool to room temperature, then cover and refrigerate.

Can be made 5 days ahead. Bring to room temperature before serving.