Preheat an oven to 180 degrees C. Grease and flour a 23cm ring tin
Whisk together the flour and baking powder in a bowl; set aside. Beat the butter and sugar with an electric mixer in a large bowl until light and fluffy. The mixture should be noticeably lighter in colour. Add the eggs one at a time, allowing each egg to blend into the butter mixture before adding the next. Beat in the vanilla with the last egg.
Pour in the flour mixture alternately with the milk, mixing until just incorporated. Pour the batter into prepared pan.
Bake until the top is golden brown and a skewer inserted into the centre comes out clean, about 1 hour 15 minutes. Cool completely before removing from the pan.