When I was an an pair in France, the lady of the house had two cake recipes she used alternately. One of them was a yoghurt cake, very simi!ar, if not identical to Maggymay's recipe above. (I still have the exact recipe somewhere but that looks about right.). It was certainly not rubbery - that is more likely caused by overworking.I
The German word for a simple sponge cake (as opposed to a cake using yeast which is what most German recipes use, or an angel cake which is the other more common kind) is Rührkuchen - stirred cake. This always reminds me that after beating the butter sugar and eggs, once the flour is added, it is just stirred in until the mixture is homogenous and then you stop.