Preheat the oven to 180'C.
Place cupcake cases into silicone or tin moulds.
Zest and juice the lemons, setting the juice aside to use in the icing.
Whisk together the butter, sugar, and lemon zest until light and creamy. Add one egg at a time and combine well. Sift the flour and the baking powder into the mixture and gently fold together. Spoon the mixture into the cupcake cakes, transfer to the oven and bake for 12 to 14 minutes.
Remove from the oven and leave to cool.
Sift the icing sugar and then beat together with the butter until pale and fluffy. Add the lemon juice and the yellow food colouring and combine well. Place the mixture into a piping bag with a star-shaped nozzle and, one the cakes are completely cool, pipe the icing on top.
«Always try to use unwaxed lemons when using the zest.»