Preheat oven to 180°C/160°C fan-forced. Grease and line an 8cm-deep, 19cm (base) square cake pan with baking paper.
Using an electric mixer, cream butter, caster sugar and vanilla in a medium bowl on medium-high speed until light and fluffy.
Add eggs, one at a time, beating to combine. Add half the flour. Stir to combine. Add half the milk. Stir to combine. Repeat with remaining flour and milk.
Spread mixture into prepared pan. Bake for 1 hour or until a skewer inserted into the centre comes out clean. Stand in pan for 10 minutes. Turn out onto a wire rack to cool. Dust with icing sugar. Serve.
