For the cakes: Preheat the oven to Gas 4/160C Fan/180C, and line a cupcake tin with 12 cupcake cases.
Put the butter, sugar and lemon zest into a medium bowl and mix with an electric whisk until light and fluffy. Add the eggs, one at a time, beating well between each addition.
In a separate bowl, mix together the flour, baking powder and salt. Then add into the wet mixture in three additions, mixing until just combined. Finally, add 1tbsp of milk and mix until combined.
Spoon the batter into the cupcake cases, filling about 2/3 of the way full, then bake in the oven for 20 minutes. Test for doneness by pressing lightly on the cupcake, if it springs back its ready! Once baked, place the cupcakes on a cooling rack to completely cool.
For the lemon syrup: Put the sugar and lemon juice into a small pan and bring to the boil. Then gently simmer until all the sugar has dissolved. Remove from the heat and set aside to cool.
For the frosting: Place the butter in a large bowl and mix with an electric whisk until lightened and smooth. Slowly add the icing sugar, beating until incorporated, and then mix on a high speed until light and fluffy. Add the lemon curd and milk, and beat until combined.
To assemble: Using a sharp knife cut a shallow cone shape out of each cupcake and fill the holes with jam. Replace the cone shapes onto each cupcake like a hat. Using a pastry brush, dab the lemon syrup over all the cupcakes. Finally, using a piping bag and star nozzle pipe the frosting over the cupcakes and garnish with a raspberry.