Preheat oven to moderate 180oC.
Brush a shallow 28 x 18 x 3 cm oblong cake tin with melted butter or oil. Line base with paper, grease the paper.
Using electric beaters, beat butter
and sugar in small mixing bowl until light and creamy.
Add the eggs gradually, beating
thoroughly after each addition. Add rind, beat until combined.
Transfer mixture to large mixing bowl.
Add carrot and walnuts. Using a metal spoon, fold in sifted spices and
flour alternately with the milk.
Spoon mixture evenly into prepared
tin, smooth surface. Bake 30 minutes or until skewer comes out clean
when inserted in centre of cake.
Leave 10 minutes before turning onto a
wire rack to cool.
To make Butterscotch Frosting -
Combine butter and sugar in a small pan. Stir constantly over low heat
until mixture boils and sugar dissolves. Simmer for 3 minutes,
uncovered, stirring occasionally.
Remove from heat, add sour cream. Stir
until combined, cool.
Using electric beaters, beat cheese in
a small mixing bowl until light and creamy.
Add cooled butterscotch mixture
gradually, beating thoroughly after each addition.
Spread frosting over cake using a
flat-bladed knife.