Heat the oven to 350°F and arrange a rack in the middle. Coat an (8-inccake pan generously with butter.
To make egg yolk batter, beat egg yolks with sugar till pale, then add in salt and oil, mix briefly till looks like mayonnaise.
To make egg white foam, beat egg whites and cream of until mixture forms soft peaks. Gradually add in sugar, beating at high speed until stiff peaks form.
Gently fold beaten egg white foam into egg yolk batter in 3 batches until fully combined.
Pour batter into tube pan. Tap the pan a few times on table top to get rid of any trapped air bubbles in the batter.
Bake in preheated oven at 350F for 30-40 minutes or until cooked. (When lightly pressed, the cake will spring back)
Immediately upon removing the cake from the oven invert the pan (turn upside dowand place on a bottle or flat surface so it is suspended over the counter.
Let cool completely before removing the cake from pan.