Cook the peaches down in a large, non-reactive pot, using a potato masher to help them break down and release their juice. Add the vanilla bean seeds and the pod so that the vanilla flavor will infuse all the peaches.
After approximately 20 minutes over medium heat, the peaches should be fairly well cooked down. Remove the vanilla bean from the pot (making sure to squeeze all the goodness from it). If you like your sauce chunky, leave as is. If you want a smoother consistency, puree with an immersion blender.
Taste and add sugar to achieve your desired sweetness. I found a happy, flavorful place at 3 cups, but depending on the innate sweetness in the peaches, you might be able to stop at 2 cups. Or you might need to add more. It’s up to you.
Pour peach sauce into pint jars, leaving a bit more than an inch of headspace. Add 1 tablespoon of lemon juice to each jar and stir in with a chopstick or plastic spoon. Wipe rims, apply lids and process for 15 minutes in a boiling water canner.
If you want to make butter from some of the sauce, reserve 6-8 cups of sauce and cook down in a slow cooker (making sure to add 1 tablespoon of lemon juice for every two cups of sauce at the beginning of cooking).