Preheat the oven to 180°C, gas mark 4, grease and line the base of a 23cm cake tin with a circle of baking parchment.
Place the walnuts into a food processor and blitz until you have a flour like consistency.
Separate the eggs into 2 mixing bowls.
Whisk the egg yolks, lemon zest and caster sugar with an electric hand whisk until pale and creamy, then whisk the egg white to stiff peaks.
Mix the blended walnuts into the egg yolks, then fold in the egg whites.
Spoon the cake mixture into your prepared cake tin, place on the middle shelve of the oven, and bake for 35-40 minutes (or until cooked in the centre and risen).
Meanwhile, peel the pears and cut in half, scooping out the core with a melon baller or teaspoon, and bruise the cardamom pods.
Add the peeled pears, saffron, cardamom pods, lemon juice, caster sugar and water to a medium sized saucepan over a low heat and poach the pears for 15-20 minutes, or until soft and infused.
Slice the cake into 8, and serve each slice with a poached pear on the side and a blob of Greek yogurt or crème fraiche.