Gâteau en papier (paper wrapped cake)

Instructions

1. Preheat the oven to 160 °C and line a 20 cm square tin with greaseproof paper, letting it overhang the edges.
2. Separate the whites from the yolks. Mix the yolks with half the sugar, the oil, milk and vanilla until smooth.
3. Sift the flour with the baking powder and a pinch of salt, then add it to the yolk mixture all at once.
4. Whisk the whites with the lemon juice into stiff foam, then gradually add the remaining sugar until firm peaks form.
5. Fold one third of the whites into the batter to lighten it, then gently fold in the rest with a spatula.
6. Pour into the tin and tap it gently on the work surface to release large bubbles.
7. Bake for 30 minutes, until golden and springy to the touch. Let it cool slightly in the tin before unmoulding.