Preheat oven to 350°
Wash the apples, and core with a pairing knife. Scrape the bottom of the core with a spoon, making sure to not put a hole through the bottom.
Combine the oats, cranberries, cinnamon, vanilla, salt, butter and 3 Tbsp water in a large bowl. Mix all ingredients with your hands, pressing the butter into the oats until it becomes sticky.
Put the apples in a deep baking dish & pour 1 cup of water on the bottom.
Liberally spoon the filling into the apples up to the top. Cover with foil & bake for about an hour, until fork tender.
Serve, and top with ice cream.