Prepare the apples. Peel and core the apples. Then cut them roughly into medium-sized chunks. (Once cut you should have about 5½ cups.) Add them to a medium-large soup pot. Add the vinegar, sugar, water, vanilla, cinnamon, cardamom and salt.
Cook. Place the pot over medium heat and bring to a boil. Immediately cover and reduce the heat to low. Let this simmer until the apples are very tender, about 30 minutes.
Blend, Cook. Pour the contents of the pot into a blender or food processor and blend until smooth. Now pour it back into the pot, this time uncovered, and bring it to a boil and then immediately reduce the heat to low and let it simmer until it's super aromatic and thick, about 10 minutes. If it's splattering (which is likely), you can put the lid on, but askew, so the apple butter is partially exposed.
Cool. Let it cool to room temperature and then store in an airtight container in the refrigerator. (It should keep for about a month this way, or in the freezer for up to 6 months.)