Melt the butter and let it cool down. Heat 100 ml milk and 50 ml water, dissolve yeast. Mix 250 g flour and 1 tsp salt. Knead in yeast milk and butter until everything comes off the bowl rim as a smooth dough. Cover and allow to rise for about 30 minutes.
Knead the yeast dough once again. Roll out to a circle (approx. 34 cm Ø) on a little flour. Fold down halfway and place in a greased baking dish (30 cm Ø) or springform pan (28 cm Ø). Press on the edge. Cover and leave to rise for 15-20 minutes.
Peel and chop the onion. Grate cheese. Mix 50 g flour and 400 ml milk in a pot until smooth, bring to the boil. Simmer onion in it for 5 minutes while stirring. Stir in cheese, remove pot from heat. Whisk eggs and cream, add. Season with salt, pepper and nutmeg
Pour the cheese cream mixture onto the pastry base and smooth it down. Bake in the hot oven (electric range: 200 °C / fan oven: 175 °C / gas: level 3) on the lowest rack for 35-40 minutes. Cover if necessary in the last 10 minutes. Serve cheese cake hot or lukewarm