Preheat the oven to 170°C/325°F/gas mark 3 and butter a 20cm/8 inch springform cake tin.
Beat the butter and caster sugar together in a bowl until pale and fluffy. Finely grate the zest of 1 orange, add to the sweetened butter, and then gradually beat in the egg yolks, followed by 2 tablespoons of flour and the dessert wine.
Lightly fold in half the ground almonds, followed by half the remaining flour. Next fold in the remaining ground almonds, then the last of the flour.
Whisk the egg whites in a clean, dry bowl until they form firm peaks. Quickly and gently fold them into the cake mix, then spoon the mixture into your cake tin and place in the centre of the oven.
Bake for 50 minutes, or until a skewer comes out clean. Turn out and place on a cooling rack over a deep-rimmed plate.
Using a potato peeler, finely pare the zest of the lemon and the remaining half orange. Put the zest, granulated sugar, dried chillies and 100ml/3½fl oz of water into a small pan.
Place over a low heat to dissolve the sugar, then simmer gently for 10 minutes. Cover, remove from the heat, and leave to infuse. Meanwhile squeeze the juice from 1½ oranges and the lemon and set aside for later.
As soon as the cake is turned out of its tin, return the syrup to the heat and bring to the boil. Add the fruit juices and vodka, and strain the warm liquid into a jug.
While the cake is still warm, prick it all over with a fork and then drip the syrup into the cake until it is completely covered. Decorate.