Preheat your oven to 350 degrees F.
In a 12×8 oval baking dish, arrange the peeled and sliced Granny Smith apples.
Mix together granulated sugar, cinnamon, and nutmeg. Ensure everything is well combined and toss it over the apples.
In a medium bowl, blend flour, oats, baking powder, brown sugar, butter, and salt. Cut with a fork or pastry cutter until crumbly.
Take the streusel topping and spread it in a single layer over the apples.
Bake for 30-35 minutes or until the top turns a beautiful golden brown.
Serve it up with a drizzle of salted caramel, a sprinkle of sea salt flakes, and a generous scoop of vanilla bean ice cream.