Puree the bananas and blueberries with the hand blender or in a blender. Then mix the fruit pulp well with the other ingredients.
Grease a loaf pan with oil and sprinkle thinly with flour. Pour in the dough and bake in the preheated oven at 200 ° C (top / bottom heat) for about 35 - 40 minutes.
Dust the cake with powdered sugar or cover it with a glaze.