Preheat oven to 180 degrees C. Grease a 23x33cm tin.
In a large bowl, mix together margarine and sugar until smooth. Mix in yolks. Stir in flour and baking powder alternately with the milk.
In another bowl, beat egg whites until doubled in volume. Fold beaten whites into the dough. Spread into a greased 23x33cm tin. Slice bananas over the top of the dough. In a small bowl, mix together the 2 tablespoons sugar and the cinnamon; sprinkle over bananas.
Bake at 180 degrees C for 30 to 35 minutes or until a toothpick inserted into the centre comes out clean. Allow to cool.