For the linzer eyes, crumble butter with flour-soda mixture. Add sugar, vanilla sugar, lemon zest, egg yolks and rum. Let rest in the refrigerator for at least 1/2 hour.
Then roll out on a floured board and cut out round circles, cut out another circle/star in the center of half of the circles.
Bake over medium heat. Let cool, spread the circles with apricot jam and put the holey circles on top.