Creating this delightful Taiwanese Castella Cake is straightforward. Follow these steps to ensure perfection:

1. Preheat Oven: Preheat your oven to 320°F (160°C). Prepare a 7-inch round cake pan by greasing it and lining the bottom with parchment paper.
2. Separate Eggs: Separate the egg whites from the yolks into two different bowls.
3. Mix Wet Ingredients: In the bowl with the yolks, add the milk, vegetable oil, and vanilla extract. Whisk until well combined.
4. Sift Dry Ingredients: In another bowl, sift together the flour, baking powder, and a pinch of salt.
5. Combine Mixtures: Gradually add the dry mixture to the wet mixture, stirring until smooth and well combined.
6. Whip Egg Whites: In a clean bowl, beat the egg whites using an electric mixer until soft peaks form. Gradually add the sugar while continuing to beat until stiff peaks form.
7. Fold Mixtures: Gently fold one-third of the whipped egg whites into the batter to lighten it. Then, carefully fold in the remaining egg whites until no streaks remain.
8. Pour into Pan: Pour the batter into the prepared cake pan, smoothing the top with a spatula.
9. Bake: Bake in the preheated oven for 25-30 minutes or until the cake is golden brown and a toothpick inserted into the center comes out clean.
10. Cool: Once baked, remove the cake from the oven and let it cool in the pan for about 10 minutes. Then, transfer it to a wire rack to cool completely before serving.

By following these steps, you’ll create a Taiwanese Castella Cake that is both fluffy and delicious.