Make a yeast starter: Heat the milk for the dough to about 110°F (43°C). Stir in one tablespoon of sugar and instant dry yeast. Leave in a warm place; in about 10–15 minutes, light brown foam with bubbles should form on the milk surface.
Start making a yeast dough: Heat the butter in the microwave for 30 seconds or melt it on the stovetop. The butter cannot be hot! In a large mixing bowl, add the flour (I recommend sifting it through a sieve beforehand), the melted butter, egg yolks, vanilla, salt, remaining sugar, and the yeast starter.
Knead the dough smooth. First, use a wooden spoon to mix the dry ingredients with the wet ones in a bowl. Once the dough has come together into a crumbly mass, turn it out onto a floured work surface. Knead a soft dough that is a little sticky with your hands. If it sticks too much to your hands or the work surface, sprinkle it with a bit of flour and work it into the dough. The whole kneading process takes about 10 minutes and may require a bit of physical work if done by hand!
Let the dough rise for an hour in a warm place. I let the dough rise in an oven with a pot of hot water on the bottom and the door shut.
In the meantime, make poppyseed filling. Pour the milk into a saucepan and add the ground poppy seeds, sugar, vanilla, grated lemon zest, and crushed cloves. Bring to a boil on the stove, then turn the heat down to low and let it simmer for 15 minutes, stirring every so often. Allow the poppy seed filling to cool completely.
Roll out the dough into a 30x12-inch rectangle (50x30cm). The dough should not be overly thin! Spread the cooled poppy seed filling evenly over the surface of the dough, leaving about 1 inch (2.5 cm) around the edge free.
Fold the dough over the filling from both sides. Basically, you create a simple roll.
Prepare your bundt cake pan. Carefully grease the inside with solid fat (e.g. Crisco) and dust with fine, taste-neutral breadcrumbs or flour.
Put the folded dough with the filling into the prepared bundt pan so that it fills all the space around the pan evenly. Allow for a second rise in a warm place, this time for 45 minutes.
Preheat the oven to 325°F (165°C) and set an oven rack in the middle position. Bake the cake for 1 and ¼ hours. If it starts to turn golden brown on the surface near the end, cover loosely with foil.