Dissolve yeast in half of the milk and mix with a little flour to form a pre-dough. Cover with a little flour and let rise in a warm place at about 35 °C for 20 minutes.
Mix remaining milk, egg, yolk, salt, sugar, lemon zest and 50 g liquid butter, add pre-dough and remaining flour and knead with dough hooks until smooth. Cover and let rest again for about 20 minutes.
Form a roll from the yeast dough on a floured work surface. Divide into approx. 15-20 pieces of equal size. Form a small ball from each piece and flatten slightly. Fill each with a teaspoon of apricot jam and seal. Dip in remaining melted butter. Layer in a prepared ovenproof dish and let rest, again covered, for 20 minutes.
In the meantime, preheat the oven to 180 °C.
Bake the Buchteln for 20-25 minutes, leave to cool and serve sprinkled with powdered sugar.
Preparation Tip:
Buchteln can be served with vanilla sauce or fruit topping. If you like, you can refine the jam for the filling with a little rum.