Sift the flour and place it in a bowl together with the vanilla and the baking powder.
Mix, make a well in the middle and add the oil, the sugar and the egg, lightly beaten.
Knead and when your dough looks like trahana (like crumbles) it is ready.
Peel and grate the apples coarsely and mix them with the rest of the ingredients for the filling (walnuts, sugar, cinnamon).
Brush a medium-sized baking tray with oil and spread half of the dough (pressing it down a little to make it even).
Spread the filling ot top and cover with the rest of the dough (pressing it down once again).
Brush with a little egg (for the colour) and bake for about an hour at 180°C.
When it is ready remove from the oven and sprinkle with a little icing sugar while it's still hot so that the sugar sticks.
