Place the butter in a bowl, beat in the sugar and salt. Add the eggs and continue to beat until the mixture becomes lighter in colour. Stir in the lemon zest. Mix the hazelnuts, flour and vanilla, stir into the egg mixture. Transfer 3/4 of the dough to the prepared tin and smooth down, creating a rim of approx. 2 cm.
Stir the jam until smooth, spread over the pastry base.
Mix the remainder of the dough with the flour, knead briefly. On a lightly floured surface, roll out to approx. 2 mm thick. Cut out stars using cutters, place on top of the tart, chill.
Place on a baking tray lined with baking paper, bake for approx. 35 mins. in the lower half of an oven preheated to 180°C. Remove from the oven, allow to cool slightly. Remove from the tin, slide onto a rack, leave to cool.
Decorate the stars with edible gold dust.