1. Preheat the oven to 350°F (175°C) and lightly grease a 9×9-inch baking dish.

2. In a large bowl, toss the sliced apples with lemon juice, granulated sugar, cinnamon, nutmeg and vanilla extract until evenly coated.

3. In another bowl, combine flour, rolled oats, brown sugar, cinnamon and salt.

4. Add cold butter cubes to the dry mixture and use fingertips or a pastry cutter to rub butter into the mixture until coarse crumbs form.

5. Spread the apple filling evenly in the prepared baking dish and sprinkle the crumble topping evenly over the apples without pressing down.

6. Bake for 35 to 40 minutes until the topping is golden brown and apple juices are bubbling around the edges.

7. Let the apple crumble rest for 10 minutes before serving to allow the juices to thicken slightly.