2 oranges, scrubbed and chopped (with skin); 5 eggs, separated; 200g caster sugar, 100g semolina, 1/2 teaspoon vanilla extract.
Put the chopped oranges in a small saucepan, discarding any pips. Add 1 tablespoon water, then cover and cook gently for 30 minutes or until the oranges are soft and excess liquid has evaporated. Leave to cool.
Preheat the oven to 180 C / Gas 4. Line the bottom and sides of a 23cm springform cake tin with baking parchment. Finely chop the oranges in a food processor or blender, or with a large knife.
Put the egg whites in a large bowl and whisk until they form stiff peaks. Gradually whisk in half the caster sugar, then whisk for 1 minute.
Using the same whisk, whisk the egg yolks with the remaining caster sugar in another bowl for 2 to 3 minutes or until pale and quite thick. Whisk in the finely chopped oranges, then carefully fold in semolina and vanilla extract.
Stir in 3 spoonfuls of the whisked egg white to loosen the mixture, then gently fold in the remaining whites with a large metal spoon. Transfer the mixture to the prepared tin and level the top.
Bake in the preheated oven until the cake is golden and a skewer inserted in the centre comes out clean, about 50 minutes. Check the cake after 20 minutes and again at 30 minutes, and cover lightly with foil if it is browning too quickly.
Leave the cake to cool in the tin, then turn it out, peel away the parchment and transfer to a serving plate. Enjoy!