With a hand or stand mixer knead the butter, sugar, salt and lemon peel with the dough hook. Add the egg yolks one by one.
Sieve the flour and add to the butter mixture.
Knead to a dough ball. Cover the bowl with a tea towel and leave the rest in the fridge for about an hour.
Preheat the oven to around 170°C or 338°F
Prepare your work surface with some flour. Or, use a silicone baking mat. Roll out the dough to 3mm thickness with a rolling pin. You can use a sheet of cling film over the dough or cover your rolling pin with some flour to avoid the dough from sticking to the rolling pin.
Cut out butter cookies in various shapes with your cookie cutters.
Place on a tray prepared with baking parchment.
If desired apply some egg yolk on the top with a brush. You can also add some sprinkles.
Bake for around 10 minutes. Leave to cool before transferring into a cookie tin.