Butter and line the base and sides of a 23cm round, springform cake tin. Preheat the oven to Gas Mark 4, 180°C, fan 160°C. Beat the butter and sugar together with an electric whisk until fluffy and light. Add the eggs, one by one, beating well between each addition.
Fold in the flour and salt to make a smooth batter. Fold in the vanilla extract, lemon zest and juice and 100g of the Greek yogurt. Pour into the tin, smoothing the top and bake for 50 minutes to an hour, until golden and springy on top. Spike the cake all over with a skewer.
Combine the lemon zest, juice and sugar for the drizzle and pour over the warmed cake. Set aside to cool completely in the tin.
Stir the icing sugar into the remaining 150g (5oz) Greek yogurt. Serve slices of cooled cake with spoonfuls of the sweetened yogurt.
Freezing and defrosting guidelines
Bake according to the recipe but stop before adding decoration or icing if called for. Allow to cool completely. Wrap well in clingfilm and tin foil (to prevent freezer burn) and freeze for up to 3 months.
Loosen the tin foil and clingfilm but leave to defrost in packaging at room temperature for several hours before serving.
If you wish to add icing or decoration, add them after the baked goods have fully defrosted and are at room temperature.