Preheat the oven to 350°F/ 175°C.
In a small bowl, combine the flour, salt, and baking powder. Set aside.
Beat together the butter, sugar, egg, lemon and vanilla extract until smooth.
Add the flour to the butter mixture, beating gently until everything is well combined. The dough is very soft but you can easily shape it.
Shape the cookies with your hands, giving them any shape you like. Line two large baking trays with parchment paper and place the cookies, leaving some distance between them as they will raise a lot when baked.
In a small bowl add the egg yolks and 3 tablespoons water and whisk with a fork. Brush the top of the cookies and bake in preheated oven for 15-18 minutes, until nicely coloured.
Let the cookies cool down completely and store in airtight containers for up to two weeks.
