Preheat your oven to 375 degrees F.
Start by making the apple filling. Place the sliced apples in a large bowl and toss with the lemon juice.
5 apples, 2 tablespoons lemon juice
Place an 8” cast iron skillet (or any oven-safe skillet) on the stovetop and add the butter, brown sugar, vanilla, cinnamon, and nutmeg to the skillet and mix over medium heat.
3 tablespoons butter, 2 tablespoons brown sugar, 1 teaspoon vanilla extract, 1 teaspoon ground cinnamon, ¼ teaspoon ground nutmeg
Once the butter is melted and bubbling (about 2 minutes) add the apple slices and stir to coat them in the butter mix.
Cook the apple slices for about 6 minutes, stirring occasionally.
While the apples cook, mix all the topping ingredients together in a large bowl. Use your hands to rub the butter into the flour and oats so it is evenly blended and there are no large butter pieces.
¾ cup flour, ¾ cup rolled oats, ½ cup brown sugar, 1 teaspoon ground cinnamon, ½ cup butter, softened
Sprinkle the topping over the apples inside the skillet then place the skillet in the oven.
Bake the crisp for 10 minutes. The top will be golden brown.
Serve while hot with whipped cream or ice cream.