Orange Sponge Cake

I had some oranges in the refrigerator.  Instead of juicing some, I baked an orange sponge cake instead.  This cake is easy to bake.  It had the zesty taste and is light and moist.

Ingredients (adapted from Jeannietay's blog)
8 inch baking tin

Part A
1.  6 egg yolks
2.  90 g cake flour
3.  1/2 tsp salt
4.  70ml oil
5.  100 ml orange juice
6.  1 tbsp. orange zest

Part B
1.  6 egg whites
2.  1/4 tsp cream of tartar
3.  100 g sugar

Method

Part A
1.  Beat egg yolks and oil until well combined.
2.  Add orange juice and zest.
3.  Fold in sieved flour and salt.

Part B
1.  Whisk egg whites until foamy and add cream of tartar.  Continue beating while gradually adding the sugar in 3 parts.  Beat until firm peak.

A+B
1.  Fold in 1/3 of Part B into Part A and combine well.  Gradually add the rest of Part B to Part A.  Combine until no streaks of yolk batter can be seen.
2.  Pour batter into baking tin and baked  with a water bath at 155 degree celsius for 70 mins or until stick comes out clean. .