I didn't bang the pan hard enough to release the air bubbles, hence the holes in the cake!
The recipe goes like this:-
4 eggs yolks
40g castor sugar
1/4 tsp salt
40g corn oil
1 tbsp lemon juice
110 g flour
10g custard powder
1 tsp baking powder
(sift the ingredients together)
5 egg whites
50g castor sugar
1/2 tsp cream of tartar
(use 1 tbsp lemon juice if you do not have cream of tartar)
In a bowl, whisk yolks and sugar till creamy and sugar has dissolved. Add oil, salt, yoghurt and lemon juice and whisk till combined.
Fold in sifted flour and mixed till batter is smooth and lump free.
In your mixer bowl, beat the egg whites till frothy before adding cream of tartar and continue to beat till soft peaks.
Add sugar in thirds and beat till stiff peaks.
Fold in 1/3 of the egg whites into the batter and gently mix till well combined. Pour the batter into the rest of the egg whites and gently keep folding until you can't see any streaks of egg white in the batter.
Pour batter into a 23 cm fluted pan and bang down on the table a few times to get rid of large air bubbles.
Bake at 170 deg C for 45 minutes or until golden brown. Immediately remove from oven and over turn the pan to cool completely before cutting and serve.
So moist and light!