Use a 6-quart slow cooker. Wash, peel, core, and slice the apples into quarters. Add the apple slices to your slow cooker insert.
Add the lemon juice, vanilla, brown sugar, and cinnamon (if using).
Cover and cook on low for 5-6 hours, or until the apples are quite tender. Mash with a potato masher or pulse a few times with a handheld immersion blender until the desired consistency is reached.
Serve warm or cold. (If you don’t mind adding an extra ingredient, serve topped with whipped cream – dairy-free or regular.)