Preheat the oven to 180°C/350°F. Put the butter, sugar and beaten egg into a bowl and mix together well until you get a creamy texture. Sift the flour and baking powder to get out the lumps.

Roughly mix the flour and baking powder in a bowl with a wooden spatula. Mix with a cutting action.

Spread olive oil or butter on the inside of a tart tray or cake tin, then sprinkle on a little bit of flour. Next spread the mixture in the tray, you might find it is easier to spread with some cling film/wrap. Cover the mixture with film wrap and push with fingers to spread it evenly.

To make the crumble: Add all * ingredients and mix them with your fingers. Do not knead.

Put the sliced apples on the tart texture side by side.

Then cover the sliced apple with the crumble. Bake for about 40 min, and allow to cool a little before enjoying this delicious treat!