Core and roughly chop the apples. You can peel them if you'd like, but I don't feel it's necessary, considering everything will be blended at the end. Place them in a lightly greased slow cooker.
Sprinkle the brown sugar, cinnamon, cloves, nutmeg and allspice over the apples and stir to incorporate. Place the lid on and cook on low heat for 6 or so hours.
After the 6 or so hours, the apples should be all broken down and very tender. It will resemble a chunky, rustic applesauce in texture, but it should be thicker and darker than applesauce.
Use an immersion blender to blend it right in the slow cooker bowl or transfer it to a food processor and pulse until smooth. Once its pureed, stir in the vanilla and salt.
Place it into a large shallow bowl so it can cool off. Allow it to cool completely, then place it in an airtight container (I like to use a mason jar) and store in the refrigerator for up to 3 weeks.
