01 - In a medium saucepan, combine the cranberries, granulated sugar, and water.
02 - Set the saucepan over medium-high heat and bring the mixture to a boil, stirring occasionally to dissolve the sugar.
03 - Reduce the heat to low and simmer for 15 minutes, or until the cranberries have burst and the mixture has thickened slightly.
04 - Remove from heat. For a smooth syrup, pour the mixture through a fine mesh sieve into a bowl or jar, pressing firmly to extract as much liquid as possible. Discard the solids.
05 - Stir in the lemon juice and vanilla extract, if using.
06 - Allow the syrup to cool completely; it will continue to thicken as it cools. Transfer to an airtight jar or bottle and store in the refrigerator for up to 2 weeks.