Ingredients to make 12 cupcakes

110g unsalted butter, at room temperature
225g caster sugar, preferably golden
2 large eggs, free-range or organic
150g self-raising flour, sifted
125g plain flour, sifted
90ml semi-skimmed milk, at room temperature
2 tablespoons freshly squeezed lemon juice
1 tablespoon sour cream
Grated zest of 1 lemon (1 teaspoon)

For the icing:

110g unsalted butter, at room temperature
2 tablespoons freshly squeezed lemon juice
Grated zest of 1-2 unwaxed lemons (2 teaspoons)
500g icing sugar, sifted

Preheat the oven to 180C/gas mark 4 and line a 12-hole muffin tray with the appropriate-size cupcake cases.

In a large mixing bowl cream the butter and sugar until the mixture is pale and smooth, which should take 3-5 minutes using an electric hand mixer. Add the eggs, one at a time, mixing for a few minutes after each addition.

Combine the two flours in a separate bowl and combine the milk, lemon juice and sour cream in a jug. Add one-third of the flours to the creamed mixture and beat well. Pour in one-third of the milk and beat again. Repeat these steps until all the flour and milk have been added, incorporating the lemon zest with the last third of flour. Don't worry if the mixture starts to curdle: simply add another spoonful of plain flour and beat well.

Carefully spoon the mixture into the cupcake cases, filling them to about two-thirds full. Bake in the oven for about 25 minutes until slightly raised and golden brown. To check they are cooked, insert a skewer in the centre of one of the cakes – it should come out clean.

Remove from the oven and leave the cakes in their tins for about 10 minutes before carefully placing on a wire rack to cool. Once they are completely cool, ice the cupcakes with lemon buttercream and decorate with a sugared lemon slice (you'll find pots of these in the baking aisle of most supermarkets) or a little finely-grated lemon zest.

To make the icing:

In a large mixing bowl beat the butter, lemon juice, lemon zest and half the icing sugar until smooth - this can take several minutes with an electric hand mixer. Gradually add the remainder of the icing sugar and beat again until smooth and creamy.

From "Cupcakes" by Martha Swift and Lisa Thomas (Kyle Cathie, £14.99)