In a large, deep pot set over medium heat, combine the pumpkin puree, apple juice, maple syrup, cinnamon, nutmeg, ginger, allspice, salt, and cloves. Bring to a low simmer and cook, stirring frequently, for 30 to 45 minutes or until thickened to your desired consistency. (In between stirring, partially cover the pot with the lid to minimize splattering while allowing steam to escape.) Stir in the lemon juice and vanilla.
Allow to cool a bit before transferring to an airtight container and storing in the refrigerator.
Instead of homemade pumpkin puree, you may substitute 2 (15-ounce) cans of store-bought pumpkin puree.
If you prefer sweeter pumpkin butter, feel free to increase the maple syrup. Alternatively, if you use sweetened apple juice or cider, you may want to slightly reduce the maple syrup.
You can tweak the spices to taste as well.
The lemon juice adds a brightness without actually being able to taste it. However, you may omit it if you don't have any.
This recipe splatters a lot at the beginning. I recommend making it in a big/deep pot and leaving the lid askew in between stirring to minimize splatters while still allowing steam to escape. The heat of the stove should be just enough the keep it bubbling, but it shouldn't be at a rapid boil. As the pumpkin butter cooks and thickens, the splattering should lessen.
Total cooking time will depend on how watery your pumpkin puree was to start, and how thick you'd like your final pumpkin butter to be.
FDA guidelines deem it unsafe to can pumpkin butter. It will keep in the refrigerator for 2 to 3 weeks and it's okay to freeze it (tightly sealed) for 6 months to a year.