Preheat your oven to 170C/340F.
Beat the butter, sugar and vanilla extract together until pale and fluffy, approximately 5 minutes with an electric beater.
Add in 1 yolk and beat until well combined, approximately 1 minute.
Repeat with each remaining egg yolk until well combined.
Stir the flour, baking powder and salt in a separate bowl.
Toss into the butter and egg yolks and whip on low until just combined and no dry portions remain in your bowl.
Whip the egg whites in a clean and dry bowl until stiff peaks form, approximately 9 minutes.
Fold the egg whites into the batter until smooth.
Pour evenly into the cake tin and place in the oven until golden, approximately 40 minutes or until a skewer comes out clean.
Remove and allow to cool in the tin for 10 minutes before turning onto a cooling rack.
Cool completely before slicing and serving.
Enjoy!