First put to one side the yoghurt, the vanilla extract and lemon zest, as these are for the yoghurt frosting. You want to make sure your yoghurt is nice and thick so that it holds well to the surface of the cupcakes. If it is a bit thin then you can always drain some of the water off. Take a bowl and cover with some muslin or a clean tea towel. Spoon the yoghurt onto the surface of the tea towel and then leave suspended over the bowl to drain off some of the water. 20-30 minutes should be fine so in the meantime you can get on with making the cupcakes themselves.
Pre-heat your oven to 200C. Then take the remaining ingredients and add them to a food processor and mix into a nice smooth batter. If you don’t have a food processor then you’ll have to make do with a large mixing bowl and a good whisk! Once you’ve got a consistency that you’re happy with, take your cupcake baking cases and fill each of them with batter. Fill to about 3/4’s full so as to give them some room to rise. Put them on a baking tray and into the oven for about 20 minutes or until light brown and the cupcakes are springy to touch.
Once the cupcakes are done, remove from the oven and leave to cool. Now you can sort out the frosting. Put the yoghurt in a bowl, along with the vanilla extract and mix briefly. Once cool, take the cupcakes and add a dollop of yoghurt to the top of each and spread over the surface so that you have a nice even layer. Garnish with lemon zest and serve.