Line a 12 cupcake hole tin with cases.
Preheat the oven to 180º/160ºfan.
You can do this in a mixer or by hand.
Cream together the butter and sugar until light and fluffy.
Add the eggs, the lemon juice and half the zest and mix in.
Sieve in the flour, salt and baking powder.
Add the milk and stir.
Add one tablespoon of mix into all the cases and top with a blackberry. Cover with the remaining mix and bake for 10-15minutes until golden brown.
Allow to cool on a rack before decorating.
Sieve the icing sugar into a bowl and add the water gradually to get a thick but movable paste.
Put a blob of icing over each cupcake, sprinkle with the remaining zest and stud with a blackberry.