Preheat oven to 180C/350F. Grease a deep 20cm (8 inch) round cake pan; line base with baking paper
Beat ingredients in a medium bowl on low speed with an electric mixer until just combined. Increase speed to medium; beat for about 3 minutes or until mixture is smooth and pale in colour.
Spread mixture into the pan; bake for about 1 1/4 hours. Stand cake in pan for 5 minutes; transfer, top-side up, onto a wire rack to cool. Dust cake with sifted icing sugar, if you like.