Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking dish.

In a large mixing bowl, combine the flour, oats, brown sugar, granulated sugar, baking soda, and salt. Stir in melted butter and vanilla until the texture resembles coarse crumbs.

Press about two-thirds of the crumb mixture into the bottom of the prepared dish and bake for 10-12 minutes until lightly golden.

In another bowl, toss diced apples with lemon juice, cinnamon, and nutmeg.

Once the crust is golden, layer the apple mixture evenly over the baked crust. Drizzle salted caramel sauce over the apples.

Sprinkle the remaining crumb mixture over the apple and caramel layers.

Bake for an additional 30-35 minutes, until topping is golden brown and apples are tender.

Cool for 15-20 minutes before slicing and sprinkle sea salt before serving.