Preheat your oven to 160°C (320°F).
In a mixing bowl, whisk together the egg yolks and sugar until pale and creamy.
Add the melted butter, milk, and vanilla extract to the egg yolk mixture and mix well.
Sift the cake flour, baking powder, and salt into the mixture and fold gently.
In a separate bowl, whisk the egg whites until stiff peaks form.
Gently fold the egg whites into the batter in three additions.
Pour the batter into a greased and lined baking pan.
Bake for 60 minutes or until a skewer inserted into the center comes out clean.
Let the cake cool in the pan for 10 minutes before transferring to a wire rack to cool completely.