Ingredients:
5 egg yolks
100g cake flour
50g corn oil or melted butter (I used melted butter)
60g orange juice
rind of 1 orange
5 egg whites
70g sugar
1/4 tsp cream of tartar
Method:
1. Preheat the oven to 180C. Line the moulds with parchment paper. You may use muffin trays. I used paper cups instead, by lining the paper cups with the parchment paper and then placed the cups in the holes of the muffin tray.
2. Melt butter in a microwave oven or heat over boiling water in a bowl. Lightly beat egg yolks with fork.
3. Grate rind of 1 orange and add into orange juice. Add this to the melted butter.
4.. Sift in cake flour to the orange juice mixture in a few additions, alternating with egg yolk and flour. Start and end with flour.
5.. Use an electrical mixer to beat egg whites for 3 minutes, then add cream of tartar and blend again. Pour sugar in the egg whites and blend until very stiff peaks form. Fold egg whites into the flour mixture gently with a rubber spatula just until all ingredients are incorporated. Do not stir or beat. For a better result, fold in egg whites with small amount at a time for 3 times.
6. Pour batter into cup cake molds that are already lined with baking paper. Bake at 180C for 25 to 30 minutes. Check with a toothpick to see if the cakes are done. If the toothpick comes out of the cake clean, then they’re ready. Allow the cakes to cool for a minute or two in the pan, then transfer to a wire rack to cool completely.
Note:
1. I don't have that kind of tall mould, so I used paper cups instead. I cut the parchment paper into square and try to fit it in the paper cup. I wrap the paper around the other cup, bottom up, then insert this wrapped cup into another, and remove the cup on top. After that, the lined paper cups are placed in the muffin tray holes as a support to prevent the cups from toppling over.