Mash the banana using a fork. Add a bit of lemon juice to prevent browning.

In a bowl, mix egg yolks and sugar until pale and creamy.

Add the mashed banana to the egg yolk mixture and mix well.

Add vegetable oil, milk, and vanilla extract to the mixture and mix evenly.

Sift in cake flour and baking powder, then mix until just combined.

In a separate bowl, whip egg whites while gradually adding sugar until stiff peaks form.

Fold the meringue into the banana batter in three additions.

Prepare the chiffon cake mold by spraying water (do not grease). Pour the batter into the mold and smooth the surface.

Use a chopstick to stir the batter lightly to remove air bubbles. Bake at 160°C for 30–40 minutes.

Immediately invert the mold after baking to cool completely.