Place all the ingredients except salt and vanilla extract in the slow cooker. Mix everything together, cover with lid and simmer on low for 10 hours.
Stir in vanilla extract and salt. Cook for an additional 2 hours.
Remove lid and using an immersion blender (for food processor or blender - see tip below), blend everything together. If you prefer a chunkier apple butter, you can use a potato masher to mash it all together.
Divide into jars, let cool and store in the fridge for up to 2 weeks. Alternatively, you can also freeze this for up to 2 months. At the rate the apple butter is being consumed, I think we will have to make another batch soon.
If you are using a food processor or blender, allow the apple butter to cool down a little before pureeing the apple butter in batches.
I want to show that having a food allergy does not limit your options. Read more on my blog, Frugal mom to a nut allergic child: Recipes, frugal finds, child development and food allergy management. Posts daily.