Place 3 pounds apples, peeled, cored, and diced, 1/2 cup apple cider, 1/2 cup brown sugar, Juice of half a lemon, 2 teaspoons cinnamon, 1/8 teaspoon ground cloves, 1/2 teaspoon freshly ground nutmeg, and 1/4 teaspoon kosher salt into a 3-quart slow cooker.
Cook on low for 8-10 hours, stirring occasionally.
When apples are tender enough to mash with a fork and dark, remove the lid and use an immersion blender to puree. You can also place the apples in a regular blender or food processor.
Leave the lid off and stir in 2 teaspoons pure vanilla extract. Cook for another hour or two on low until thickened to your desired consistency. Place into jars for storage.