Halve the vanilla pod and scrape out the seeds using a teaspoon. Reserve seeds and pod.
Make a caramel by placing the sugar and water in a medium sauspan and bringing it to a soft boil. To avoid crystalization brush down sides of the pan with a wet pastry brush and don’t stir the mixture. Continue to boil until mixture turns a light golden brown.
Turn down the heat to low and add cranberries to the mixture, use a wooden spoon to coat the berries with the caramel. And cover for a minute to avoid spattering
Turn heat to medium and add salt, vanilla seeds, vanilla pod and port. Stir the mixture for about 10 minutes until the texture of jam.
Transfer sauce to a bowl and let rest for 30 minutes before serving or let cool and refrigerate for up to 3 days.