Preheat the oven to 180C (160C fan-forced). Line a 12-hole medium muffi n pan (1/3 cup capacity) with paper cases. Using electric beaters, beat the butter, sugar and vanilla extract until light and
creamy. Mix through the lemon zest.
Add the eggs one at a time, beating well a er each egg. Gently fold through the flour and milk in two alternate batches. Divide the mixture evenly among the paper cases.
Bake for about 20 minutes, or until golden brown and springy when touched. Remove from the oven and transfer to a wire rack to cool completely before decorating.
To make the icing, use electric beaters to beat the butter until light and creamy. Add the icing sugar a little at a time, beating constantly. Add half the lemon juice and beat until well combined. Add the remaining lemon juice a little at a time, and tint with food colouring if you like. Using a 1 cm fluted nozzle, pipe the icing onto the cooled cupcakes. Decorate!!
Note: To make Lime Sublime cupcakes, substitute the zest of 6 limes in the cake batter and 2 tbs of lime juice in the icing. For Clockwork Orange cupcakes, try using the zest of 2 oranges in the batter and 2 tbs of orange juice in the icing.