Wash the sultanas, drain and steep them in orange juice.
Place the wheat flour and sugar in a mixing bowl, mix and make a hole in the middle. Dissolve the yeast in the warm milk and pour into the hole. Using a fork, stir the yeast-milk mixture with a little flour to form a soft pre-dough. Cover the bowl and leave in a warm place for around 20 minutes.
Add the butter, eggs, vanilla sugar, salt and lemon zest to the pre-dough in the bowl and knead to a smooth dough using a handheld mixer (dough hook) for about five minutes at high speed. Cover again and let it rest for another 45 minutes.
Knead the almond slivers and the soaked sultanas into the mix and use a dough scraper to scoop and fill the dough into a well-greased and floured cake tin. Now cover the dough and let it rest for another 60 minutes.
Preheat oven to 175 °C (top/bottom heat).
Bake on the lowest rack for 10 minutes, then reduce the baking temperature to 150 °C and bake for another 45 – 50 minutes. If the surface is too dark, cover with a piece of baking paper
Sprinkle with icing sugar or use 100 g of sieved icing sugar, 10 g of water and 10 g of lemon juice to make a thick icing and brush it onto the bundt cake.