for 6 portions
Put the flour and baking powder in a pile on the pastry board. Put the softened butter in pieces in the middle. Mix quickly to make a pile of "crumbs". Add to the crumbs the sugar, yolk and egg, grated lemon zest and a pinch of salt. Mix this all together quickly, make it into a ball, wrap it in a cloth and put it in the fridge to rest for 30 minutes.
Using a rolling pin, roll out the dough to a thickness of 5 mm and cut out circles slightly larger than the individual cases that you are going to use.
Put the dough into the greased, floured cases. To prevent the tarts from swelling up too much, prick the dough a few times with the prongs of a fork. Cook in a pre-heated oven at 180°C for 8-10 minutes. Take them out of the over, then remove the tarts from the cases and let them cool down. Fill the tarts with Nutella® and serve.