Start by preparing the sweet shortcrust pastry. You can do this in a food processor or by hand. Place the flour in the bowl of the stand mixer, then add a pinch of Maldon salt and the cold, diced butter. Heat until you get fine crumbs (try not to mix too much) Add the icing sugar. Then add the egg yolk and turn on again until a paste forms.
If you’re doing it by hand, work the butter into the flour with your fingers.
Transfer the dough to cling film and press it into a circle, then wrap the dough in the cling film and refrigerate for 20 minutes.
Preheat the oven to 180°C.
After 20 minutes, take the dough out of the refrigerator. Lightly dust a work surface with plain flour, then using a rolling pin, roll out into a large circle about 1cm thick and a diameter suitable for a 20cm tart tin. Lift the dough up and line the pan with it, making sure to press down firmly on the corners. Use the rolling pin to remove excess dough from above. Prick the bottom of the dough lightly with a fork. Line the bottom of the pan with parchment paper and dry beans to blind bake the dough.
Place the cake pan on the center rack of the preheated oven and bake for 15 minutes, then remove the parchment paper and beans and return to the oven for another 10 minutes. It should be slightly golden and covered with a light powder.
Remove the cake from the oven and set it aside. Now prepare the pistachio frangipane filling. Grind the pistachios until you get a fine powder. In a food processor or electric mixer, cream the softened butter with the sugar and add a pinch of Maldon salt. Beat until pale and light. Then add the eggs and beat again. Then add the crushed pistachios, the ground almonds and 1 tablespoon of regular flour and incorporate everything until you get a homogeneous mixture.
Pour the frangipane into the baked pie plate and smooth the top. Spread the cherries on top and press down very lightly. Sprinkle with slivered almonds and bake for 40 minutes until the cake is lightly browned and the frangipane has puffed up.
Remove from oven and let cool for at least 20 minutes before slicing and serving dusted with icing sugar.