Peel and core the apples and cut into small pieces. Wash the lemon in hot water, dry and grate. Then squeeze the juice of ½ lemon and pour over the apple pieces. Mix the remaining ingredients in a bowl and place in a baking dish.
For the crumble
Mix all ingredients with a spoon or the hands and spread evenly over the apple mix and bake in the oven at 170°C for 25 minutes.