Preheat your oven to 170°C and grease a 15 cm * 20 cm pan with some oil and sprinkle flour to prevent sticking.
Separate the 3 eggs into 2 bowls (egg whites and egg yolks). With your hand or electric mixer, beat the egg yolks with 1/4 cup sugar on high speed for 2-3 mins until pale and fluffy.
Add the milk and vanilla and mix again. Add the flour, baking powder and salt and switch to a spatula to mix them into the batter.
Clean your mixer and start whipping the egg whites until foamy. Start adding the remaining 1/4 cup sugar gradually until the egg whites reach stiff peaks.
Gently FOLD the stiff egg whites into the cake batter using a spatula or a spoon.
Pour the batter into the prepared pan and bake in preheated oven for 18-20 mins or until a toothpick inserted in the middle of the cake comes out clean.
When done, turn the oven off, open the oven door a bit and let the cake cool gradually for 20 mins. After that, remove from oven and poke holes in it using a fork before pouring the milk mixture on top.