Preheat the oven to 180°C.
Using a small sharp knife, remove cores from apples. Cut each apple in half horizontally and place in a greased baking dish. Add 2 Tbsp of water, cover with foil and place in the oven. Cook for 10 minutes.
Make the apple crumble topping:
While the apples are cooking, place the oats, almond meal, hazelnuts and cinnamon in a bowl. Stir to combine. Add the orange juice, half the maple syrup and lemon zest. Mix together well.
Finish the apples:
After 10 minutes take the apples out the oven. Divide the apple crumble mixture into four. Push some of this mix into the centre of each apple and then pile the rest on top. Drizzle over the rest of the maple syrup. Re-cover the apples and cook for 10 minutes. Remove the cover and continue cooking for another 10 minutes, or until the topping is golden brown and the apple is cooked through.
You could replace the oats and nuts with a pre-made natural muesli. Add in a sprinkling of sultanas or flame raisins.
Store leftovers in the fridge and eat the next day.