Cook the bacon until crisp, and reserve the fat. Chop the bacon.
Add the beans, onion, apple, apple butter, half the chopped bacon, and 2-3 tablespoons of the bacon fat to your crock pot. Give it all a stir to mix.
Cook on high for 3-4 hours. You can also cook on low for 6 hours.
Open the lid and give everything a good stir. Add the cider vinegar and taste. The sauce will seem a little thin at first, but will thicken as you stir it, and as it sits with the lid off. I like to take the lid off for the last ½ hour of cooking.
Serve the beans topped with the remaining bacon.
