Preheat your oven to 170°C (340°F) and grease a loaf tin, lining it with baking paper for easy removal.

Begin by melting the butter, either in a small saucepan over low heat or in the microwave until completely melted. Set it aside briefly to cool.

In a large mixing bowl, combine the melted butter with the caster sugar and vanilla extract, stirring until the sugar dissolves. Add in the mashed bananas and milk, blending the mixture until smooth. Once slightly cooled, add the lightly beaten egg, mixing until just combined.

Gently fold in the sifted self-raising flour, mixing only until there are no visible streaks of flour—take care not to overmix.

Pour the batter into your prepared loaf tin, spreading it evenly. If using, place the halved banana, cut side facing up, on top of the batter for a decorative finish.

Bake in the preheated oven for 35-40 minutes or until a skewer inserted into the center comes out clean. Allow the cake to rest in the tin for 5 minutes before transferring it to a wire rack to cool completely. Enjoy your moist, tender banana cake!