Preheat oven to 350 degrees F.
In a large cast iron skillet, melt the butter over medium heat.
Add the sliced apples, brown sugar, cinnamon, and nutmeg and cook until apples are slightly softened, about 8-10 minutes.
Add the caramel sauce and salt, and stir until well combined. Remove from heat.
In a medium bowl, combine flour, oats, brown sugar, cinnamon, salt, and melted butter. Stir well to combine.
Sprinkle over apple filling in the cast iron skillet. Note: you can bake the crisp directly in the cast iron skillet or transfer it to a 9x9" baking dish.
Bake in the preheated oven for 40-45 minutes, until golden brown and bubbling.
Serve topped with vanilla ice cream and drizzle with additional caramel sauce. Enjoy!