Preheat the oven to Gas 3/160C/140 fan assisted oven. Line a 12 hole muffin tin with paper cases. Place the butter in a large bowl and cream until soft. Add the sugar and beat until the mixture becomes light and fluffy.
Whisk the eggs in a small bowl and gradually add them to the butter mixture, continually stirring. Next stir in the milk and vanilla then sift in the flour, baking powder and salt and gently fold to combine.
Equally divide the mixture between the muffin cases. They should be filled 2/3 of the way. Place in the oven and bake for 20-25 minutes or until well risen, slightly golden and springy when you touch them. Allow the cakes to cool for 5 minutes and then remove from the tin and place them on a wire rack so that they can cool completely.
Now make the icing. Place the lemon juice and strawberries into a blender and blitz for 1-2 minutes until smooth. Sieve the mixture into a bowl and set aside.
In another bowl, cream together the butter and icing sugar until well combined. Add this to the fruit puree and beat continually.
Using a palette knife or the back of a spoon, spread the icing onto the cupcakes and decorate with one berry on the top.