Put the softened butter in a bowl, add the confectioners' sugar and mix well. Add the vanilla sugar, lemon zest, salt and rum. While stirring, add the yolks, then add the flour (previously mixed with the baking powder), and knead in a soft dough with the milk. Cover with a towel and leave the dough to rest in a cool place for about 1 hour. Spread the dough out, cut out circles and rings, then bake. Leave the cookies to cool an cover the circles with the jam. Sprinkle the rings with confectioners' sugar, then put them on the circles.
Cooking temperature: 180° C static oven / 160° C ventilated oven