Blend the flour with the salt and sugar. Cut the cold butter into cubes and knead them through the flour. Blend the creme fraiche and egg yolks. When a bread crumb consistency has been reached, blend with the creme fraiche and egg yolks. Knead shortly into a smooth dough and put aside in the fridge, wrapped in cling film for 30 minutes. Turn the oven to 180ºC, get the dough from the fridge, knead a little to soften and roll out into the form. Bake blind for 20 minutes, after that remove the blind filling and bake another 15 minutes or lesser or more, just to the point the cake is nice and brown. Get it off the oven and set aside to cool down.

Squeeze the lemons and cut the butter into cubes. Put hem aside in the fridge. Heat the lemon juice and mix the eggs and egg yolks with the sugar. Keep stirring until the temperature is 82ºC, when the liquid starts thickening. At that point, add the cubes of butter into the liquid. Let it cool down and pour into the cake. Make is nice and smooth with a spatula. Put in the fridge to cool down.