Lemon cupcakes

I was in need of cake last night for Sunday tea, having a large amount of lemons in my fruit bowl these seemed like the obvious choice from The Hummingbird Bakery Cookbook. As I used large cupcake cases the mix only made 9 cakes. The recipe also make a huge amount of icing so I probably reduced it by half. They were delicious. I think the cupcakes from the Hummingbird Bakery are the most successful ones I have ever made. 
 
Ingredients
Make 12
120g of plain flour
150g of caster sugar
1½ teaspoons of baking powder
2 tablespoons of grated lemon zest, plus extra to decorate
40g of unsalted butter (at room temperature)
120 ml of whole milk
1 egg

For the lemon frosting:
250g of icing sugar (sifted)
80g of unsalted butter (at room temperature)
2 tablespoons of grated lemon zest (I used the juice of the two lemons I had zested for the sponge)
A few drops of yellow food colouring (optional but pretty)
25 ml of whole milk

Method
You will need
A 12-hole cupcake tray lined with paper cases
Preheat the oven to 170°C.
Put the flour, sugar, baking powder, lemon zest, and butter in a freestanding electric mixer with a paddle attachment (or use a handheld electric whisk) and beat on slow speed until you get a sandy consistency and everything is combined.
Gradually pour in the milk and beat until just incorporated.
Add the egg to the flour mixture and continue beating until the flour is just incorporated, making sure to scrape any unmixed ingredients from the side of the bowl with a rubber spatula. Continue mixing for a couple of minutes until the batter is smooth, but be careful not to overmix.

Spoon the mixture into the paper cases until two thirds full. Bake in the preheated for 20-25 minutes, or until the cake bounces back when touched. A skewer inserted in the center should come out clean.
Let the cupcakes cool slightly in the pan before turning out into a wire rack to cool completely.
When the cupcakes are cold, spoon the lemon frosting on top and use extra lemon zest to decorate accordingly.

For the Lemon frosting:
Beat together the confectioners' sugar, butter, lemon zest (or juice), and food coloring in a freestanding electric mixer with a paddle attachment (or use a handheld electric whisk) on medium-slow speed. Continue until the mixture is well-mixed.
Turn the mixer down to a slower speed and slowly pour in the milk. (I didn't use milk as I used the juice from the lemon)
Once the milk has been incorporated, turn the mixer up to high speed.
Continue beat until the frosting is light and fluffy; this should take at least 5 minutes.