2oranges, washed250 gmcaster sugar½ tspground cardamomPinchof ground cinnamon300 gmblanched almonds, finely ground in a food processor1 tspbaking powder5eggsFor dusting:pure icing sugarTo decorate:candied oranges and clementinesOrange-blossom yoghurt300 gmthick natural yoghurt40 gm(¼ cup) pure icing sugar3 tsporange-blossom water, or to taste
Place oranges in a large saucepan, cover completely with cold water and bring to the boil over high heat. Cover with baking paper and a plate to weigh oranges down, then cook until oranges are soft (2-2½ hours). You may need to top up with extra water to keep oranges covered. Drain, cool, then remove and discard calyx and seeds from oranges and coarsely chop.
Preheat oven to 180C. Process oranges, sugar and spices in a food processor until finely chopped. Transfer to a bowl, add almonds and baking powder and set aside.
Meanwhile, whisk eggs in an electric mixer until pale (3-5 minutes), add orange mixture and whisk to combine (10-20 seconds). Pour into a buttered and baking paper-lined 22cm-diameter spring-form pan and bake until golden an inserted skewer withdraws clean (50 minutes). Cool on a wire rack for 5 minutes, then release sides of pan and cool completely.
Meanwhile, for orange-blossom yoghurt, combine ingredients in a bowl and refrigerate until required.
Decorate cake with candied fruit. Serve with orange-blossom yoghurt to the side.