Preheat your oven to 160°C (320°F). Grease and line a cake pan.
In a mixing bowl, whisk egg yolks and half of the sugar until pale and creamy.
Add melted butter, milk, and vanilla extract to the yolk mixture. Mix well.
Sift in cake flour and fold gently to combine.
In another bowl, whisk egg whites until foamy. Gradually add the remaining sugar and beat until stiff peaks form.
Gently fold the egg whites into the yolk mixture in three additions.
Pour the batter into the prepared cake pan and smooth the top.
Bake for 35-40 minutes or until a skewer inserted into the center comes out clean.
Let the cake cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.