Preheat your oven to 350 degrees F. Gathering all the ingredients before making your cake.
Separate egg yolks and egg white into two different large bowls.
Start working on the egg white bowl first: Beat egg whites until stiff peaks form (this should take about 5 minutes) with an electric mixer. Once stiff enough, add ⅕ cup powdered sugar gradually five separate times while beating continuously at high speed until the mixture thickens. Add sugar gradually while whipping until the mixture becomes thick and pale yellow. Set aside.
In the egg yolks bowl, pour coconut oil and milk. Then, sift the cake flour, cornstarch, and baking powder into the batter. Beat until smooth batter forms.
Now, slowly fold the egg white bowl into the egg yolk bowl. Mix it with a spatula 45 times. (I know, I counted it, lol). Do not use a mixer or overmix!
Brush a layer of oil on the cake pan, and pour the cake batter into the cake pan. Here comes the most crucial part, drop the cake pan on the kitchen counter a few times until you no longer see the bubbles. Doing this gives you a smooth surface for the finished sponge cake.
Put the cake pan into the oven and bake it for 30 minutes at 350 degrees F. The finished color should be light golden brown. You can test with a toothpick inserted in the center, which should come out clean. It is ready when the cake’s edge separates slightly from the pan. Please allow your cake to cool completely before you remove it from the pan. Please allow your cake pan to cool completely on a wire rack before you remove the cake from the pan.
Serve with your favorite topping, or serve it as it is! Enjoy!