Pre-heat the oven to 175°C (350℉). Grease a small (18cm or 7") spring-form pan.
Beat the butter and sugar together until light.
Add the eggs, one at a time.
Sift the baking powder with the flour and add to the wet ingredients.
Add the milk and mix until just combined.
Pour into the prepared tin and bake for around 30-35 minutes.
Remove from the oven and allow the cake to sit in the pan for 10 minutes, then turn out onto a wire rack. Let it cool completely.