Bring to a simmer over medium heat, stirring until the sugar dissolves.
Simmer for 3 minutes, then remove the pan from the heat.
Stir in the vanilla bean paste.
Make sure to add vanilla bean paste off of the heat, to preserve it's flavor.
Cool, then transfer to a clean jar or bottle. Refrigerate.
Notes
Store vanilla bean simple syrup in a clean, airtight container in the refrigerator for up to 2 weeks. Discard the syrup if you notice mold, an unusual smell, or other signs of spoilage.