I honestly don't know where I got this recipe. I have been making this cake for about 25 years. I personally don't like bananas, the feel of raw bananas is icky! This is the only way I will eat bananas. Gen this recipe is for you as I remember how much you love banana cake.
I don't know about your house however in my house when a banana gets one little brown spot on it, apparently it becomes inedible! I find the bananas languish in the fruit bowl getting browner and browner until I do something about it.
This cake is a bit of a one pot wonder type cake, chuck it all in a mixer and mix.
When Jonathan was little it was fun to get him to mash the bananas, I used to stick a bowl in front of him with the peeled bananas and say "Squish 'em with your fingers" it must be a boy thing, he used to mush them through his fingers with glee.
125g room temp butter
1/2 cup castor sugar
1 1/2 cup self raising flour
1 tspn bi carbonate soda
2 tblspn milk
1 1/2 cup mashed banana
Place all the ingredients in a mixer and mix for 30 seconds to a minute or until combined.
Place batter in a greased and floured cake tin or loaf tin. Bake at 180C for an hour. Check with a skewer if clean remove from the oven if still wet bake for longer.
Remove from the oven and allow to cool.