Prepare the Batter – In a bowl, whisk together milk, vegetable oil, egg yolks, 20g sugar, vanilla extract, and salt until smooth. Sift in the cake flour and mix until combined.
Whip the Egg Whites – In a separate clean bowl, beat egg whites with lemon juice until frothy. Gradually add 50g sugar and beat until stiff peaks form.
Fold Gently – Using a spatula, carefully fold the whipped egg whites into the batter in three additions, making sure not to deflate the air.
Bake the Cake – Pour the batter into an ungreased chiffon cake pan and tap gently to remove air bubbles. Bake in a preheated oven at 320°F (160°C) for 35–40 minutes until golden.
Cool Upside Down – Immediately invert the pan and let the cake cool completely before removing it from the pan to retain its structure and fluffiness.