What you need for 1 cake:
Melt the butter on a slow heat. Mix the sugar into the eggs, while the butter is melting. Now stir the melted butter into the egg and sugar mixture and gradually add the flour. Finally, pour in the Pur Natur yoghurt and the blueberries.
Place the mix into a cake tin that has been greased with butter.
Put it in a hot oven at 180° C for 30 minutes.