Peel, core and slice all the apples.  Then place them in the bottom of a slow cooker.

Top the apples with the sugar, cinnamon, nutmeg, cloves and salt.  Stir to combine all the ingredients.

Cover and cook on low for 10 hours or on high for 5 hours, stir the mixture halfway through the cook time.

After the cook time, turn the crock pot off and let the mixture cool slightly.

Then use an immersion blender to puree the mixture until smooth (or transfer the mixture to a blender and blend until smooth).

After pureed, stir in the vanilla extract.  Move the mixture into jars or an airtight container.  Then the apple butter is ready to enjoy!