Heat the oil

• Warm the vegetable oil in a saucepan over low heat until hot but not smoking.
• Sift the flour, cornstarch and salt into a bowl.

Make the batter

• Pour the hot oil over the dry ingredients and whisk until smooth.
• Add the milk, egg yolks and vanilla extract and whisk to a smooth batter.

Whip the egg whites

• Beat the egg whites with the lemon juice until foamy.
• Add the sugar gradually and whip to soft to medium peaks.

Fold together

• Fold a third of the meringue into the batter to loosen it.
• Gently fold in the remaining meringue until just combined.
• Pour into the lined cake pan and tap out air bubbles.

Bake in a water bath

• Place the cake pan in a larger baking dish and pour in hot water.
• Bake at 150 °C until golden and set, then cool before slicing.