Melt the butter and set aside to cool. Mix the flour, baking soda and salt.
In a second bowl, the two types of sugar are now mixed with the cold but still liquid butter until creamy. Now add the egg and yolk and mix the mixture well. Then lemon juice, zest, flavor and vanilla extract can be added and stirred.
Finally, the flour mixture is added. Now you can knead! The dough can be a bit dry and crumbly, so you can add 1 - 2 tablespoons of milk.
Now balls the size of golf balls are rolled, placed on a baking sheet lined with baking paper and gently pressed down. They are baked for 10-12 minutes at 160 ° C.