Step 1 Slice the vanilla bean in half lengthwise and use a paring knife to scrape the seeds and pulp of one-half of the bean into a medium saucepan. Add half of the vanilla pod, the sugar and the water and bring to a boil over medium-high heat.
Step 2 Meanwhile, remove the large white veins, or pith, from the tangerine segments.
Step 3Reduce the heat to low and add the tangerines to the syrup. Simmer the fruit until the tangerines look a little puffy and shiny, 3 to 5 minutes.
Step 4Strain the mixture over a bowl and discard the vanilla pod. Return the liquid to the pan and reduce over medium-high heat until it's slightly thickened and coats the back of a spoon.
Step 5Allow the syrup to cool completely and gently stir in the tangerines.