Preheat the oven to fan-forced 160°C/320°F or 180°C/350°F top-bottom heat and line a baking sheet with parchment paper.
Add butter to a mixing bowl and use a hand mixer fitted with whisks to beat until light and fluffy. Gradually add sugar, egg, vanilla sugar, lemon zest, and salt, beating in between. Continue beating until the sugar is dissolved and you have one unified mass.
Attach a dough hook to your hand mixer. Add four, baking powder, and milk and knead until a shiny dough forms.
Press out the dough through a spritz cookie press. Cut dough off at desired length and transfer the spritz cookies to your baking sheet. Bake in the oven for approx. 6 – 8 min., removing the cookies once they are cooked but still light in color.