- Preheat oven to 180°C. Place the apple, sugar, lemon juice and cinnamon in a large bowl and mix to combine. Transfer to a 1.5-litre-capacity ovenproof dish.
- To make the crumble topping, place the flour, sugar, cinnamon, oats and butter in a large bowl and mix until just combined.
- Spoon the crumble mixture over the apple and place the dish on a large baking tray. Bake for 40–45 minutes, or until the crumble is golden and the apples are soft. Serve with vanilla ice-cream.