To make the crust, mix the oil, water and flour in a large bowl.
In a cup, add the bicarbonate of sodium with the lemon juice and mix well.
Add the mixture to the bowl, together with the vanilla extract.
Separately, mix together the 7 tablespoon of oil and flour, and add it to the rest of the ingredients.
Knead the dough well for about 5 minutes, this should be elastic and should not stick to the bowl at all.
Shape it into a ball, cover with clingfilm and refrigerate for at least 2-3 hours.
To make the filling, peel and grate the apples, and add them to a pan together with the cinnamon and vanilla sugar.
Leave to cook on a low to medium heat until all the juice has been absorbed and the apples have turned into a brown colour.
Remove from the heat and allow to cool completely.
Roll out the dough and cut 4 circles to cover to bottom of 4 tartlet dishes. Sprinkle semolina all over the bottom dough layer, add a layer of apple filling, sprinkle some more semolina.
For the top layer, cut the dough into thick strips and arrange them one vertically, one horizontally.
Bake in the preheated oven at 200 degrees C (390 degrees Fahrenheit) until golden brown.
Remove from the oven and allow to cool completely. You may sprinkle some powdered sugar on top, but that's totally optional.