Preheat the oven to 170℃ fan bake.
Begin by dissolving the baking soda in the milk in a small cup.
Prepare a square tin.
Cream the softened butter, sugar and vanilla until light and fluffy (walk away and do a small task - it is best when forgotten about).
Add the eggs one at a time - mixing well after each additon.
Mash the bananas and add them to the mixture, along with the lemon juice. Mix until smooth.
Add in the baking soda and milk.
Next fold in the self raising flour.
Pour the batter into the prepared tin and bake for 35 minutes until a skewer comes out clean. Allow to cool for 15 minutes until turning out onto a wire rack to cool completely.
Once cool, ice the cake.