Wash the apples thoroughly. Peel them if you prefer, although leaving the skins on is fine.

Remove the cores and cut the apples into large chunks.

Place the apple pieces in your slow cooker along with the sugar, vanilla extract, cinnamon, salt, and cloves. Stir to distribute the ingredients.

Cover and cook on high for about an hour, or until the apples begin to soften.

Reduce the heat to low and continue cooking for several more hours, stirring occasionally, until the apples are very soft and have developed a rich, brown color.

The apples should release their natural juices as they cook, so there's usually no need to add water. If they seem to be browning too quickly or sticking to the bottom, reduce the heat or add a small splash of water to prevent burning.

Once the apples are very soft, use an immersion blender to purée them until smooth. You can blend them directly in the slow cooker, taking care not to splash the hot mixture.

If you don't have an immersion blender, carefully transfer the cooked apples to a regular blender and process in batches, following your blender's instructions for handling hot foods.

If the apple butter is still too thin, continue cooking on low with the lid off, stirring occasionally, until it reaches your desired consistency. Keep in mind that it will thicken slightly as it cools.

Taste the apple butter and adjust the sweetness or spices to your liking. If it's too sweet, add a little lemon juice to balance the flavor.

Transfer the finished apple butter to clean jars or other suitable containers. Allow it to cool before refrigerating or freezing.