Coarsely chop 100 grams of pecans. Peel bananas and cut into fine slices. Beat the eggs, sugar and oil. Stir in bananas and vanilla sugar briefly. Mix baking powder, flour, salt and cinnamon. Quickly stir into the egg mixture, stir in buttermilk, fold in chopped pecans.
Pour into a greased, sugar-spread box form (1 1/4 litre capacity; 26 centimetres long). Sprinkle with 50 grams of pecans. Bake in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for one hour. Remove from the oven and leave to rest in the mould for 15 minutes. Turn out of the mould and dust with icing sugar shortly before serving