Cream sour cream, granulated sugar, 3 eggs and oil in a bowl and then mix with flour, hazelnuts, cocoa and baking powder.
Grease baking pan, dust with flour, pour in mixture and bake at 180 °C for about 45 minutes (up to 55 minutes with convection oven).
Let the cake cool briefly and turn it over.
Preparation Tip:
Serve the cake with a dollop of whipped cream.