Preheat the oven to 180 ° traditional heat. Peel the apples, core them and cut them into cubes (neither too big nor too small).
Place the apples in a bowl then add the flour, brown sugar, cinnamon and lemon juice. Coat them well then place them in a small gratin dish (mine is 27x17cm).
In another bowl, combine the oatmeal, flour, baking powder, brown sugar, cinnamon, salt and warm melted butter. With a spatula or by hand, mix to obtain a sandy mixture.
Crumble this crumble over the apples. Bake for about 40-45 minutes. The top should be lightly golden. Out of the oven, let cool before eating plain or with a scoop of vanilla ice cream ...
Notes
Can be stored at room temperature if tasted within 24 hours (cover it with aluminum foil).Otherwise, it can be stored in the refrigerator for about 4 days, protected with cling film.