Grease and line 9-inch (23-cm) round baking pan with parchment paper.
Preheat oven to 160°C/320°F (you may add in a tray of water, about 2 cups, to increase the humidity, which helps cake bake evenly).
For meringue: Whisk egg whites over low speed until large bubbles are formed. Add in cream of tartar, whisk until small bubbles are formed. Add in sugar gradually, whisk until stiff peak (the peaks will point straight up and hold).
Combine egg yolks, sugar and salt, beat until thick. Add in corn oil, beat until combined. Add in grated orange zest and orange juice, mix until well blended.
Sift together cake flour, baking powder and baking soda. Sift again into egg yolk mixture, mix until combined.
Add meringue to batter in 3 batches, mix gently using a balloon whisk. Fold gently until well mixed using spatula, then tap mixing bowl on countertop for a few times to burst large bubbles. (Reminder: Do it quick but gentle to avoid deflating the meringue. Scrape the bottom of mixing bowl with spatula and fold over, repeat folding motion until just well mixed.)
Pour batter into baking pan, tap baking pan again for a few times.
Bake at 160°C/320°F for 25 minutes, then increase to 180°C/355°F and bake for another 10-15 minutes, or until fully cooked (wooden stick inserted in the center of the cake comes out clean).
Once remove from oven, drop the baking pan from 1 foot high onto countertop (to minimize shrinkage).
Unmould Orange Sponge Cake and set aside on wire rack until completely cooled.