Preheat oven to 350°F. Place apples, salt, spice, and vanilla extract in a 11x 14-inch shallow baking dish. Cover with apple juice and swirl to mix.
Cover with aluminum foil and roast the apples for 30-40 minutes or until soft. Remove foil. Using a fork or a potato masher, mash the apples, adjust the spices if necessary and cook for another 1-1.5 hours, stirring the mixture every 30 minutes, until deeply browned and thickened.
Dot with butter and let it melt in. You may puree for a smoother consistency.
Let the apple butter cool completely before storing. Keep in an airtight container in the fridge for up to 2 weeks.