Preheat your oven to 375°F (190°C). Butter an 8x8 inch baking dish.

In a large bowl, toss the sliced apples with lemon juice. In a separate small bowl, whisk together 1/4 cup brown sugar, 1 tbsp flour, 1 tsp cinnamon, and nutmeg. Pour over the apples and toss to coat. Spread evenly in the prepared dish.

In another bowl, combine the rolled oats, 1/2 cup flour, 1/2 cup brown sugar, and 1/2 tsp cinnamon. Add the cold cubed butter. Use a pastry cutter or your fingers to cut the butter into the mixture until it resembles coarse crumbs.

Sprinkle the topping mixture evenly over the apple filling.

Bake for 40-50 minutes, until the topping is golden brown and the filling is bubbly.

Let the apple crisp cool for at least 15 minutes before serving. This helps the filling set. Serve warm.