Dissolve the yeast in a little lukewarm milk, add the sugar, pour into the sifted flour and mix gently. Let the dough rise for about 15 minutes. Then add the rest of the milk, butter, 1 egg, salt and lemon zest and knead everything into an elastic dough. Cover and let the dough rise in a warm place until it has doubled in volume. Then knead carefully, shape into a long roll and wrap it into a pretzel. Let rise for another 15 minutes.
Brush with the beaten egg yolk before baking. Bake at 200 ° C top / bottom heat for 25-30 minutes until golden yellow.