The butter, kept at room temperature, is mixed with sugar and a pinch of salt. Incorporate the beaten egg, lemon peel and baking soda with a little lemon juice, then water and flour.
We start to knead the dough to obtain a homogeneous composition.
Wrap the dough in cling film and store in the refrigerator for approx. an hour, after which we take it out of the fridge and prepare the tart. From the dough we will keep a small part for the crumble, and we will spread the rest in a round sheet that we will place in the tart bowl greased with butter and lined with flour, so that the edges come out of the bowl easily. We can use our fingers to spread the dough well on the walls of the bowl.
We wash and slice the apples. We will put two apples on the large grater, and we will slice the other two into slices about 0.5 cm thick. We will lightly fry the grated apples on the fire, together with a spoonful of sugar, cinnamon and a spoonful of breadcrumbs.
Sprinkle a spoonful of breadcrumbs on the dough, over which we will place the composition of grated apples (after it has cooled slightly). Over the composition of grated apples we will place the apple slices, forming a spiral. Sprinkle 1-2 tablespoons of vanilla sugar and ground cinnamon on top.
Bring the edges of the dough to the center, partially folding the apple spiral. From the remaining dough we will break small pieces with which we will cover the fruits from the tart.
Bake the tart in the preheated oven, at the right heat, for 35-40 minutes.
Turn off the heat, remove the pan from the oven and let the tart cool, then we can slice and serve.