Preheat your oven to 180ºC/160ºC Fan/Gas 4. Line a 12 hole muffin tin with cupcake wrappers. I like to use cupcake wrappers from Purple Cupcakes. In a stand mixer, or large bowl using a hand mixer, cream together the Stork/butter and caster sugar until light and fluffy.
Crack the eggs into a jug and lightly whisk. Add the eggs to the butter and sugar mix, then the lemon extract, juice and zest, and mix until well combined.
Add the flour, mixing until only just combined - don't overmix. Half fill the cupcake wrappers.
Make a small well in the centre of each cupcake and add a teaspoon of lemon curd to the middle.
Cover the lemon curd with the remaining cupcake mixture, making sure each cupcake wrapper is approximately 2/3 full.
Bake for around 18-20 minutes until ready. A skewer or toothpick inserted into the top of the cupcake will come out clean when they're ready. Remove from the oven and allow to cool on a wire rack.
While the cupcakes are cooling, make the buttercream. Add the ingredients to the bowl of a stand mixer and mix together well.
Pipe the buttercream onto the cooled cupcakes in a swirl, then top with some more lemon zest.