This recipe comes from a lovely book, Classic Turkish Cookery by Ghillie Basan. I have adapted it, substituting the lemon zest for the 2 tbsp of dessicated coconut and 2 tbsp of sultanas she includes. She suggests that you might use a 450 g loaf tin; I used a 20 cm springform tin. The cake had a pleasingly foamy texture, with a squidgy centre.
More expert bakers than I would know what difference it makes to follow the procedure below with the eggs and sugar rather than creaming the butter and sugar.
225 g self-raising flour
1/2 tsp baking powder
175 g butter
175 g caster sugar
175 g thick yoghurt
1 tsp vanilla essence
Zest of 1 lemon
Cut a disc the size of the base of your tin in a sheet of greaseproof paper; put a little butter on the base, and fix the paper on top. Assemble the tin.
Sift the flour and baking powder into a bowl.
Melt the butter and leave to cool. Whisk the eggs and sugar until they are light and fluffy. In a separate bowl, beat the melted butter into the yoghurt, and add the mixture to the eggs and sugar. Stir in the vanilla and lemon zest. Fold in the flour.
Spoon the mixture into the tin, and bake in the centre of a gas mark 4/180 C oven. My cake was ready in 45 minutes (an inserted skewer came out clean). Loosen the cake from the sides, release it from the tin, and leave to cool. Wrapped in a layer of paper and then foil, it keeps for several days.