Serves 8 3 oranges 1 tbsp orange blossom water olive oil, for greasing 5 eggs, separated 250g caster sugar 250g ground almonds 1 tsp baking powder 4 tbsp icing sugar 1 tbsp cold water 20cm round cake tin baking paper
Place 2 of the oranges, unpeeled and whole, in a large saucepan and cover with boiling water. Simmer, with a lid on, for 1½ hrs, then drain. Once cooled, halve the oranges and remove and discard any pips. Place the oranges in a liquidiser, blend until a puree, then set aside. Preheat the oven to 180°C/160°C fan/gas mark 4 and grease and line the cake tin with baking paper. In a large mixing bowl, whisk together the egg yolks and caster sugar, using an electric whisk, for 2-3 mins until very smooth and creamy, and doubled in volume. Stir in the ground almonds, orange puree and baking powder.
In a clean mixing bowl, and with a clean whisk, whisk the egg whites for 3-4 mins until stiff. Gently fold them into the almond mixture until completely incorporated. Transfer the batter to the prepared tin and bake for 55 mins-1 hr until an inserted metal skewer comes out clean. Allow to cool in the tin.
Remove the cake from the tin and discard the baking paper, then place the cake on a serving plate. Peel the remaining orange with a knife, leaving the whole orange intact, then slice it horizontally very thinly. Cover the top of the cake with the orange slices. In a small pot, combine the icing sugar with the orange blossom water and cold water, to make a runny icing. Drizzle the icing over the cake, then allow to set, and serve.