First mix the room temperature butter with the confectioner's sugar. We can mix it by hand or with a stand mixer, until we have a smooth texture.
Add the 4 egg yolks, vanilla extract, lemon zest and mix again.
Now you can add the cake flour, almond flour, baking power and slat and mix until you have your cookie dough.
Let the dough chill for 1 hour or overnight into the fridge covered. This way will be easier to form your cookies.
Extend the dough with a roll on a surface with flour and using a cookie cutter from your cookies.
Plan your cookies on your cookie tray or oven tray. You can use some baking paper too.
Preheat your oven 356º Fahremheit (180ºCelsius).
Bake for 10-15 minutes, until they brown.
Let them cool, fill them with jam and decorate with confectioners sugar.