Core and dice the apples. No need to peel!
In the bowl of a large slow cooker, combine the diced apples, pumpkin, brown sugar, cinnamon, ginger, clove, nutmeg, apple cider, and lemon juice. Cover and cook on low 8 hours, or high 4 hours.
Using an immersion blender, puree the now-soft apples until very smooth. Alternatively, if you haven't listened to me up to this point, you can transfer small batches to a traditional blender and puree.
Cover the slow cooker and heat an additional 1 hour.
To store, transfer to heat-safe jars or containers. Apple butter keeps in the refrigerator for up to a week, or the freezer up to three months. This recipe is also PERFECT for canning, but I'm not an expert so search around the interwebs for methods.