In the basin of the Instant Pot, combine the apples, brown sugar, cider, cinnamon, salt, cloves, and nutmeg.
Close the lid, turn the lever to seal, and set to Manual High pressure for 60 minutes. When cooking time is up, allow the pressure to release naturally for 20 minutes, then remove the lid.
Add in the vanilla extract.
Using an immersion blender, blend the mixture until very, very smooth.
The apple butter will seem very thin, but the pectin from the peels will make the mixture thicken dramatically once cooled (similar to making jam). To test the thickness of the apple butter, place a spoonful of the apple butter on a small bowl or saucer, and then place in the freezer for 5-10 minutes until chilled. Run your finger through the chilled apple butter to test for thickness. If it’s thick enough for your liking, store the apple butter in an airtight container in the refrigerator.
If you want to thicken the apple butter more, turn the Instant Pot to the Slow Cooker setting on High, cook for 2-3 hours with the lid off, and then repeat the freezer thickness test to ensure you’re happy with the thickness.