*Sift all ingredients together. Preheat the oven to moderate 180C.
2
Brush a shallow 28x18x3cm oblong cake tim. Line base and sides with paper and grease the paper.
3
Beat butter and sugar with electric beaters until light and creamy. Add the eggs gradually, beating throughly after each addition. Add rind and beat until combined.
4
Transfer mixture to large mixing bowl add carrots and walnuts. Using a meal spoon fold in (*) sifted ingredients alternatively with the milk. Spoon mixture evenly into the preheated tin, smooth surface. Bake 30min. or until skewer comes out clean. Leave 10min. Before turning into wire rack to cool.
5
The butterscotch frosting: Combine butter and sugar in a small pan. Stir constantly over a low heat until mixture boils and sugar dissolves. Simmer for 3min. uncovered stirring occasionally. Remove from heat and add sour cream, stir until combined. Cool. Using electric beaters beat cream cheese until light and creamy, add cooked butterscotch mixture gradually, beating throughly after each addition. Spread frosting over cake using a flat bladed knife. Storage: 3days in airtight container or 2 months in freezer with no icing.