Preheat the oven to 375°F (190°C) and lightly grease a 9x9-inch baking dish with butter or non-stick spray.
Peel, core, and slice the apples, keeping the slices thin but sturdy. Place them in a large mixing bowl.
In a small bowl, mix the melted butter, granulated sugar, brown sugar, cinnamon, nutmeg, vanilla, and salt until combined.
Pour the mixture over the apples and toss to coat them well.
Sprinkle the cornstarch over the apples and toss again to make sure it’s coated well.
Spread the apples in the prepared baking dish, making sure they’re in a single layer.
Bake for 35-40 minutes, stirring once halfway through, until the apples are tender and the sauce is thick and caramel-like.
Let the apples cool for about 5-10 minutes before serving. Enjoy!