01 - Place the cranberries, granulated sugar, and water into a medium saucepan. Drop in the strip of orange peel, if using.
02 - Set the saucepan over medium heat and bring to a gentle simmer, stirring occasionally. Cook for 10 to 12 minutes until most of the cranberries have burst open and the mixture has thickened.
03 - Remove the saucepan from heat. Pour the mixture through a fine mesh sieve set over a bowl, pressing firmly on the berries with a spoon to extract as much liquid as possible. Discard the solids.
04 - Stir in the vanilla extract if using. Allow the syrup to cool completely, then transfer to a clean bottle or jar and seal tightly. Refrigerate for up to 2 weeks.