Combine the granulated and brown sugars along with the salt and spices in a medium bowl then mix together and set aside.
Add the apples to your slow cooker then pour the sugar mixture over and mix to coat the apples. Cover and set slow cooker to 10 hours.
After 10 hours pour in your vanilla and mix then set to two hours, cooking uncovered to evaporate some liquid.
If you like chunky apple butter use a potato masher to break the apples down. For a totally smooth apple butter pulse in a food processor or immersion blender until desired consistency is reached.
Notes
Taste your apples before adding them to your slow cooker. If they're super sweet you can decrease the sugar by 1/4 cup. If they're very flat you can add a squeeze of lemon juice.
You can simmer the apple butter in a pot over low heat to reduce excess water if you want to have total control over consistency.
To make this on your stove instead of a slow cooker add the ingredients to a large pot over medium-low heat and cook while stirring frequently for about an hour until the apples are softened then process the apples into a puree and continue to cook at medium low until they caramelize and thicken.
Make sure to refrigerate containers if you aren't going through the canning process.