01 - Combine the cranberries, granulated sugar, and water in a medium saucepan. Add the orange peel strip if desired for a citrus note.
02 - Set the saucepan over medium heat and bring to a gentle simmer, stirring occasionally. Continue cooking for 10 to 12 minutes until most of the cranberries have burst and the mixture has thickened.
03 - Remove the saucepan from heat. Pass the mixture through a fine mesh sieve, pressing the berries firmly to extract all the liquid. Discard the solids for a smooth syrup consistency.
04 - Stir in the vanilla extract if using. Allow the syrup to cool completely, then transfer to a sealed bottle or jar. Refrigerate for up to 2 weeks.