In a slow cooker, add the apple, brown sugar, lemon juice, cinnamon, ginger powder, cayenne pepper powder, and salt. Stir to combine then cover and cook on high for 4 hours. Stir once or twice during that period.

Once the apples have cooked, turn the slow cooker to low, uncover the slow cooker, and process the apples to a puree (or leave it slightly chunky - your choice) using a hand blender.

Add the vanilla extract and stir to combine.

Taste the apple butter and add additional spices to get your perfect flavor. This is a perfect opportunity to up the cayenne spice if not spicy enough. Note - the apple butter will get spicier as it sits, so if you plan on keeping it around for a few days, consider balancing the heat.

Cover the apple butter again and - keeping the slow cooker on low - cook the apple butter for an additional hour, stirring once during the time.

Remove the apple butter from the slow cooker and allow it to cool for half an hour before serving. Or for best flavor, jar the apple butter and allow it to chill in the refrigerator for 2 to 3 hours prior to serving (allowing the spices to meld).