01 - Place the cranberries, granulated sugar, and water into a medium saucepan. Add the orange peel strip if desired for a citrus accent.
02 - Set the saucepan over medium heat and bring to a gentle simmer, stirring occasionally with a wooden spoon. Continue cooking for 10 to 12 minutes until most of the cranberries have burst open and the mixture has thickened noticeably.
03 - Remove the saucepan from the heat. For a smooth, refined syrup, pour the mixture through a fine mesh sieve, pressing firmly on the berries with the back of a spoon to extract all available liquid. Discard the solids left behind.
04 - Stir in the vanilla extract if using. Allow the syrup to cool to room temperature before transferring it to a clean, sealed bottle or jar. Refrigerate for up to 2 weeks.