200gbutterroom temperature (or dairy free hard margarine - add a little extra icing sugar if using)
2-4lemon zestoptional, but I love zest in my buttercream
For the lemon curd
Firstly (if making yourself) make your lemon curd (you might want to do this ahead of time so it has plenty of time to cool down). Add your eggs to a saucepan and whisk (hand whisk, not electric!) to combine.
Add the rest of your ingredients and pop it on a medium heat. Whisk your mixture, allowing the butter to melt and then continue to mix for a further 10 minutes (approx) until the lemon curd starts to thicken slightly. (Don't let it boil)
Leave to cool completely before popping it into a glass jar to thicken further in the fridge. It's then ready to use for the cakes!
For the cupcakes
Preheat your oven to 180C (160C Fan) and place cupcake cases into your tin.
Add all your ingredients into a large mixing bowl and beat together with an electric hand whisk until smooth and combined.
Spoon the mixture evenly between your cupcake cases, about 2/3rds full. Place in the oven for 20-25 minutes until a skewer comes out cleanly and they are golden on top.
Allow them to completely cool on a cooling rack.
For the buttercream
For the buttercream, ensure your butter is soft and at room temperature. I find it takes a good hour out of the fridge to soften, but never let it go too soft! Place your butter into a stand mixer and mix on a medium speed for about 5 minutes until the butter has gone a lot more pale in colour.
Add your icing sugar gradually. I add it in 2-3 stages and beat for about 3 minutes between each addition. Start your mixer slowly to save your kitchen from a real icing sugar mess, but then increase the speed to medium / high for each of your 3 minutes.
Add in your lemon zest and lemon juice (add half and then add the second half after its incorporated). Beat for a further 3 minutes and it should then be done. Ensure it's the right thickness - it should be if you've beaten it for long enough. However, if it's too thick you can add a tiny amount of milk or extra lemon juice. And if too thin, sieve in a little extra icing sugar - this might be the case for dairy free buttercream.
For the assembly of the cupcakes
Once the cupcakes and lemon curd are cool, you need to make little holes in your cupcakes to fill with the lemon curd. I use one of my piping nozzles to gently push into the centre of the cupcake and remove a bit. You could use a knife and remove a little too. Just make sure you don't go too deep as you need some of the cake beneath to hold the filling!
Spoon some lemon curd into the hole you've made in each cupcake.
Spoon your buttercream into a piping bag with a large star nozzle. Then pipe your buttercream on top.