Peel and cut out the cores of the apples then dice into one inch pieces. Place diced apples in a bowl as you work on each apple and add the lemon juice to the diced apple pieces to keep from browning. Once all the apples are diced add to slow cooker with the lemon juice.

Add in the apple cider and apple cider vinegar on top of the apples then add the brown sugar and apple pie spice, or your own spice blend (see notes).  Stir well then set the slow cooker to high. Cook for 2-3 hours until bubbling. Stir again then set the slow cooker to low and prop the lid slightly ajar with a spatula or wooden spoon to allow steam to escape. 

Cook for 6-8 hours until the apple butter has greatly reduced, deepened in color and is easy to mash with a spoon. Check for taste and consistency, if you want thicker bring back to high and get bubbling for another hour or so and stir once an hour, keeping the lid ajar.

Once the apple butter is a thick consistency, make the caramel sauce.

Heat the butter, brown sugar and maple syrup in a saucepan and stir until butter is melted and sugar is completely dissolved. Bring to a boil and boil for 4 minutes, without stirring.  At 4 minutes remove from heat ( take completely off the burner) and stir in the salt and heavy cream, whisking until completely mixed in. Return to heat and cook for one more minute.  Pour the caramel sauce into the apple butter and stir. 

If you want a completely smooth apple butter transfer to a blender to blend smooth or pass through a food mill or chinois. You can do this before adding the caramel sauce if you are blending the entire batch or after if only making half the batch smooth. 

At this point the caramel sauce is ready to be transferred into jars. The sauce will keep well in your refrigerator a few weeks up to 6 months frozen.