Place the apples and water in a 5 qt slow cooker. Set on high and cook for three hours.
Puree apple mixture until smooth using an immersion blender or in a food processor.
Stir in maple syrup, brown sugar, and vanilla extract. Continue to cook on high for another three hours. The sauce should thicken and darken and mound up on a spoon. It won't spread out across the spoon when you scoop some up.
Prepare jars for canning.
Pour apple butter into hot, sterilized jars. Fit with metal lids and bands. Place in hot water bath and process for 10 minutes.
Remove jars from water bath and allow to cool undisturbed overnight on a towel on the counter, spacing them at least an inch apart. Once cool, remove bands and check lids for seal. Store in the pantry.
Nutritional values are approximate and are based on 1/12 of the recipe, about 1/2 cup. Refrigerate opened leftovers promptly and use within 4 days.