Prepare water bath canner by filling to 3/4 full of cool water. Add the jars and bring to a boil. Turn down and keep to a simmer.
Combine the pear quarters and cranberries in a heavy stockpot. Add in the scraped vanilla bean pods (reserve the seeds for later).
Cook over medium heat, stirring frequently to prevent burning, until the cranberries begin to pop, about 5-10 minutes.
Add the sugar, lemon juice and vanilla seeds. At this time, you can remove the bean pods carefully - mixture is very hot.
Continue cooking and stirring occasionally, until most of the cranberries have popped and the juices have been released from the pears.
Cook until the mixture reaches the desired thickness, about 20 minutes.
Test doneness by dropping a spoonful onto a plate. Let cool for a minute, then tilt the plate sideways. If the jam appears to keep its shape, it's done. If it separates, it needs more cooking time. (test and cook as needed)
Using an immersion blender (or upright blender or food processor), puree the mixture to desired consistency.
Spoon into hot jars, leaving 1/2 inch headroom. Wipe rims, place the lid and put into canner.
Bring the water to a boil and process for 10 minutes.
Remove to a protected countertop. After 1 hour, test the lids and place any unsealed jars into the refrigerator. Let the remaining jars cool another 2 hours. Label and date.
