Pre-heat the oven to 350 ºF (175 ºC) and grease a round cake pan (alternatively, you can line it with baking/greaseproof paper). I've used a round cake pan 8 1/3 inches in diameter.
Bake in the pre-heated oven at 350 ºF (175 ºC) for 25 to 30 minutes, or until a toothpick comes out clean and the edges are a dark golden brown colour. (Note 3)
Note 1: Pureeing the bananas is recommended (not just mashing them) as the final batter should be as smooth as possible to ensure a nice regular "zebra" pattern.
Note 2: The amount of caster sugar depends on how sweet you want your cake to be. 3/4 cups gives you a pleasantly afternoon tea-sweet cake that you could get away with eating for breakfast, 1 cup gives a this-is-definitely-a-dessert cake (which I suppose you can still eat for breakfast... there's bananas in there... fruit... ergo, suitable for breakfast).
Note 3: If the top of the cake starts browning too quickly, cover it with aluminium foil until baked.
Recipe by The Loopy Whisk (www.theloopywhisk.com).