Instructions

1. Grease and line a 23cm round spring form cake tin. Put the whole oranges in a large pan of water, bring to the boil and simmer for 1 hour, until soft. Remove, cool, halve and remove the pips.
2. Preheat the oven to 180C/350F/gas mark 4.
3. Whizz the oranges to a puree in a food processor. Beat in the eggs, polenta, almonds and sugar.
4. Pour into the tin and sprinkle with the demerara sugar. Bake for 1 hour, until the cake is risen and golden.
5. For the drizzle, dissolve the sugar in 100ml hot water in a ban. Boil for 5 minutes without colouring. Remove from the heat and cool briefly before adding the Grand Marnier and zest.
6. Cool the cake in the tin, then turn out and drizzle with the syrup.