Preheat the oven to 170˚C and sift the flour.
Grease and line the bottom and sides of the cake pan with baking parchment.
Crack the eggs into a large bowl.
Fill a larger bowl with water heated to about 50 to 60°C. Place the bowl with eggs over it, so that the bottom is submerged in the water. Heat the mixture until it is warm to the touch.
Start beating the eggs with an electric mixer at low speed. Gradually add sugar while beating the eggs. Continue beating on high speed for about 8 minutes.
Reduce the speed to low and beat for a further 2 minutes until the batter becomes foamy. The mixture should be pale yellow, almost white, and reach the ribbon stage. (Remove the bowl from the warm water.)
Sift the cake flour directly over the egg mixture. Gently fold in the sifted flour with a spatula, while rotating the bowl, so that it is fully incorporated.
Take a few spoonfuls of this mixture and stir it into the oil, mix thoroughly and add it back, folding lightly to incorporate.
Very gently fill the prepared cake pan with the batter. Rap the bottom of the pan against your work surface, to release any trapped air bubbles.
Reduce the temperature to 160℃ and bake for about 30 minutes until the top is light brown and the skewer comes out clean.
Turn the cake upside-down on a wire rack and let the cake cool for 5 minutes in the pan. Re-invert back onto the cooling rack and let it cool completely.
Remove it from the pan and then remove the parchment paper. Allow it to cool completely before cutting. Cover it with a clean cloth so that it doesn't dry out.