1.Preheat oven to 180°C. Grease 20cm x 30cm lamington pan.
2.In a small bowl, beat butter, sugar and egg with an electric mixer until light and fluffy. Stir in combined sifted flours.
3.With lightly floured hands, press mixture evenly over base of prepared pan. Place pan in freezer for 15 minutes, then bake in moderate oven about 15 minutes or until browned lightly; cool.
4.To make topping, combine ingredients in medium bowl and mix well.
5.Place lemon butter in small bowl and whisk until smooth. Spread lemon butter over cold base, then sprinkle with topping.
6.Bake about 35 minutes or until browned. Cool in pan before cutting.
This recipe can be made a week ahead; store in an airtight containerNote