Preheat the oven to 350°F. Coat the inside of a 9x13 baking dish with butter or nonstick spray. Set aside.

For the filling, melt the butter in a large stock pot over medium heat. Add the apples, brown sugar, cinnamon, and salt. Stir to coat the apples. Bring to a simmer and cook for 10–15 minutes. Stir occasionally, until the apples soften and the juices reduce into a dark, caramel-like sauce. Remove from heat.

In a small bowl, whisk together the cornstarch, vanilla and lemon juice. Pour the cornstarch slurry over the apples and stir until the filling thickens, about 1–2 minutes. Transfer the apple filling to the prepared baking dish.

For the topping, in a large bowl, whisk together the flour, granulated sugar, brown sugar, baking powder, baking soda, cream of tartar, cinnamon, and salt.

Pour in the melted butter, heavy cream, and vanilla. Stir with a fork just until a thick, shaggy dough forms. The mixture should look uneven and slightly crumbly with a few dry bits of flour.

Using your hands, scatter clusters of dough over the apple filling, leaving some of the filling visible between the pieces.

Bake for 40–50 minutes, until the topping is golden brown and the apple filling is bubbling around the edges. Let the cobbler rest for 15 minutes before serving. The filling will continue to thicken as it cools. Serve warm with vanilla ice cream and caramel sauce.