Add flour to a large bowl, form a well and add sugar, yeast, and half of the warm milk.

Mix ingredients in the well gently, cover with a clean kitchen towel and allow to sit for about 10-15 min.

Add salt and rest of the milk. Knead for about 5 min. on low speed.

Add soft butter and knead until the dough is soft and elastic.

Cover with a clean kitchen towel and allow to proof for about 1 hour.

Butter a springform pan (9-inch) and place the dough into the pan. Spread out evenly to cover the bottom and pull up on the sides to form a rim. Leave about ½ inch from the top.

Let proof in pan for another 30 min. to 1 hour.

In the meantime, finely cube the onions and bacon.

Fry in butter until translucent over medium low heat. Make sure to stir constantly to avoid browning.

Sprinkle the bacon-onion mix with flower, mix well and set aside to cool down.

In a large bowl whisk the eggs.

Add heavy whipping cream and sour cream and mix well.

Add the cooled down onion-bacon mixture to the bowl.

Salt and pepper to taste and mix well.

Pour mixture on top of the dough and sprinkle with caraway seeds.

Cut the 2 tbsp. of cold butter into very thin slices and spread evenly on top of the cake.

Bake in pre-heated oven for 40-50 min at 400F.

Serve hot or lukewarm.