Preheat oven to 350°F (175°C). Grease and flour a 9-inch round pan or line with parchment.

Beat egg yolks with half of the sugar until pale and thick. Mix in vanilla, warm milk, and oil or butter.

Whip egg whites until frothy, then gradually add remaining sugar and beat to stiff peaks.

Sift flour and salt over yolk mixture in three additions, folding gently. Fold in one-third of the whites, then the rest.

Pour batter into pan, smooth the top, and bake for 25–30 minutes until golden and set.

Cool 10 minutes in pan, then turn out onto a rack to cool completely.