Use an electric beater to beat butter, vanilla and 100g (1/2 cup) sugar in a bowl until pale and creamy. Add eggs, 1 at a time, beating well after each addition. Stir in sour cream mixture and combined flour, in alternating batches. Spoon into pan. Bake for 35-40 minutes or until a skewer inserted into centre comes out clean. Cool in pan for 15 minutes.