Preheat oven to 160°C (320ºF). Place the butter, sugar and vanilla into the bowl of an electric mixer and beat until light and creamy. Add the eggs and beat well. Fold through the flour and spoon into a 20cm x 30cm cake tin lined with non-stick baking paper. Top with the nectarine and blueberries and sprinkle with icing sugar. Bake for 1 hour or until cooked when tested with a skewer. Cool in tin. Serves 10.