Place the butter in a bowl. Add the sugar, salt and vanilla seeds, beat using the whisk on a hand mixer until the mixture becomes lighter in colour. Stir in the flour, mix to create a dough, do not knead.
Transfer the dough to the prepared tin, press down flat. Score the surface of the dough into 16 rectangular fingers using the back of a knife, prick holes in the dough using a wooden skewer. Sprinkle with sugar, cover and chill for approx. 30 mins.
Approx. 35 mins. in the centre of an oven preheated to 180°C. Remove from the oven, allow to cool slightly, remove from the tin, cut into fingers, leave the shortbread to cool on a rack.