Place the sugar, butter and lemon zest in a bowl and beat until really light and fluffy. Now beat in the eggs a little at a time. If the mixture looks curdled, add a tablespoon of the flour. Fold in the remaining flour, the polenta, ground almonds and lemon juice.
Spoon the mixture into the prepared tins and
For the lemon icing, mix the icing sugar with a drop of lemon juice and stir energetically until smooth. The icing should be thin but should hold its own weight and drizzle in nice fluid lines. We test this on a saucer first. If too thick, add more juice. Using a spoon or a plastic bag snipped at one corner, zigzag the icing over the loaves. Sprinkle with the raspberries and serve.