In a medium pot, mix together the cranberries, sugar, and lemon juice. Bring to a boil over medium heat, stirring constantly to ensure the sugar doesn’t burn or caramelize, about 15 minutes. Once the sugar is dissolved and the berries look glossy, stir in the lemon zest and pear puree. Scrape the vanilla seeds into the mixture, stir, and add the pod. Remove from the heat and let cool. Remove the vanilla pod before serving.