Simmer water and 1/2 cup sugar until dissolved, then add vanilla bean if desired. Remove from heat and coat cranberries with syrup. Let steep for 10 minutes.
Strain cranberries, reserving syrup, and let them dry on parchment for 45 minutes to 1 hour until shiny and sticky.
Roll dried cranberries in remaining sugar to coat evenly.
Enjoy immediately or store in a container with rice to absorb moisture, keeping for up to 2-4 days.
Notes
Store cranberries in a cool, dry place and toss with more sugar if they weep after a few days.