Preheat the oven to 190°C (375°F), gas mark 5.
Put the apples in a bowl with the lemon juice, water and 110g of the soft brown sugar, toss together.
Then place in greased ovenproof baking dish.
Mix together the melted butter with the remaining sugar, and then stir in the flour and oats until evenly mixed.
Pour over apples. Bake for 35 min or until the top is golden brown and bubbling.
Serve warm with a spoonful of Crème friache or Greek yogurt.