Preheat the oven to 175°C. Grease and line a 20cm-square cake pan.
Sieve all purpose flour, 2 teaspoon of baking powder and ⅛ teaspoon of salt all together and set aside.
Process butter and sugar in for 2 minutes until light on a medium speed.
Add 3 eggs one at a time, pulsing after each until just combined.
Whip on medium speed until smooth and creamy.
Add 1.5 teaspoon of vanilla extract and whip to combine.
In 3 alternating batches, add sieved flour and milk, pulse on low speed just to combine. After adding 3rd batch flour and milk, combine everything with a spatula in cut and fold method. This step helps to get a proper butter cake without being too spongy.
Pour cake batter into pan and bake for 55-60 minutes until a skewer inserted in centre comes out clean.
Cool for 5 minutes, then turn onto a rack to cool completely.