Preheat the oven to 180C/350F/gas mark 4
Use a 15cm/6 inch cake tin.
Cream the margarine with the sugar until light and fluffy. Stir in the carrot and orange rind. Fold in the flour, baking powder and cinnamon. Add milk and mix well. Transfer the mixture to the greased cake tin with a circle of greaseproof paper in the base. Bake for 1 hour in the preheated oven. Remove the cake from the tin and set it to cool on a wire rack. Meanwhile, melt the coconut over a low heat. Stir in the orange juice and spread the mixture evenly over the cake.