Preheat oven to 180ºC. Grease and line deep 20cm round cake tin with baking paper.
Cream butter, vanilla and sugar until light and fluffy. Add eggs one at a time, beating well after each addition. Sift flour and baking powder together. Fold into creamed mixture. Add sufficient milk to give a soft dropping consistency.
Spoon mixture into the cake tin and spread evenly.
Bake for 35 to 40 minutes or until cake springs back when lightly touched.
Leave in tin for 10 minutes before turning out onto a wire rack to cool. When cold dust with icing sugar.