Preheat oven to 180 degrees C (350 degrees F). Using a kitchen brush grease very well a large bundt pan (for best results I pour into the pan ½ tbs all purpose flour and 1-2 tbs oil and use the brush to mix them and spread the mixture all around).
In a bowl combine the two kinds of flour, cornstarch and baking powder.
In a blender or food processor puree bananas and yogurt until smooth.
In a large mixing bowl beat together honey and vegetable oil at high speed of the mixer until smooth. Add eggs and vanilla extract and continue beating at a lower speed until the mixture becomes homogeneous. Add banana mixture and beat few more seconds, until well combined. Using a rubber spatula carefully fold in the flour mixture until completely absorbed in the batter.
Pour small quantity of the batter in a cup and add in the cocoa powder. Mix well until the cocoa is completely absorbed. This part will be used to make the marble effect of the cake.
Pour half of the uncoloured batter into the prepared pan. Spoon the cocoa batter on top. Cover with the remaining batter. If you want to make the cake even more marble-like, you can go with 3 layers of uncoloured batter with 2 layers of cocoa batter in between them.
Bake for 50-60 minutes or until a wooden skewer inserted in the centre comes out almost clean.
Let the cake cool until room temperature before frosting it.
Coconut Cream Cheese Frosting:
Combine all ingredients and mix well until homogeneous. Frost the cake all around.