1. Preheat the oven to 180°C, gas mark 4. Grease and line the bases of 8 x 150ml pudding moulds with butter and baking parchment. Place the pistachios into a food processor and blitz until ground to a powder.
2. Beat the egg yolks with the caster sugar in a stand mixer until light and creamy then, with the motor running, slowly add the ground pistachios and semolina, followed by the salt, melted butter, lemon zest and marmalade. Beat until smooth.
3. In a separate bowl, whisk the egg whites until forming stiff peaks. Gently fold the whites into the nut mixture in three batches, to retain as much air as possible.
4. Pour the batter into the prepared moulds and bake for 20 minutes until golden and a skewer inserted into the cakes comes out clean.
5. Meanwhile, warm the syrup ingredients together in a pan with 100ml of cold water over a high heat. Bring to the boil, then reduce the heat and simmer for 10 minutes or until reduced and syrupy. Discard the vanilla pod.
6. Remove the cakes from the oven and while still warm and in their tins, slowly pour half of the syrup over them. Leave the cakes to cool completely before turning out onto plates.
7. Stir the orange blossom water and orange zest through the yogurt. Sprinkle the cakes with the chopped pistachios, drizzle with the remaining syrup and serve with the yogurt.