Preheat your oven to 375°F (190°C) and grease a 9x13-inch or 2.5-quart ceramic baking dish with butter.

In a large mixing bowl, toss the sliced apples with granulated sugar, dark brown sugar, lemon juice, flour, cinnamon, nutmeg, allspice, and vanilla until thoroughly coated. Transfer into the prepared baking dish and spread into an even layer.

In a separate bowl, whisk together 1 ½ cups flour, ⅓ cup sugar, baking powder, baking soda, and salt.

Cut the cold cubed butter into the flour using a pastry cutter or your fingertips until pea-sized crumbs form.

Pour in the cold buttermilk and vanilla extract, stirring gently with a fork just until a soft, moist dough forms (do not overmix).

Drop generous spoonfuls of the biscuit dough evenly over the spiced apple filling, leaving small gaps for the caramel sauce to bubble through. Sprinkle the tops with turbinado cinnamon sugar.

Bake at 375°F for 40 to 45 minutes, until the biscuit topping is deep golden-brown and the spiced apple juices are thick and bubbling vigorously around the edges.

Remove from the oven and let cool for 15 minutes to allow the natural pectin syrup to thicken before spooning warm into bowls with a generous scoop of vanilla bean ice cream.