Pre-heat oven to 180C / 360F. Prepare a muffin tin with cupcake cases.
Top and tail and quarter the lemon. Add lemon quarters to the Thermomix bowl with the butter. Mix 7 seconds / speed 8.
Add the sugar, eggs, flour, baking powder and baking soda. Mix 20 seconds / reverse / speed 4.
Use a large cookie/ice cream scoop to divide the mixture into the muffin cases.
Bake in the oven for 20 minutes until a knife comes away clean when inserted into the middle of a cupcake.
Allow to cool for a couple of minutes then transfer to a wire cooling rack to cool completely.
Once cool, take a knife or teaspoon and scoop out a small section from the middle of the cupcakes.
Fill the holes in the cupcake with lemon curd. You can use a piping bag or teaspoon to do this. Replace the section of cupcake and press down so that you have a smooth top to the cupcake. It doesn't matter if it looks a bit messy, you will be covering it up.
To make the meringue, first mill the sugar in a clean dry mixing bowl for 10 seconds / speed 9. Set aside. Now clean and dry the mixing bowl thoroughly. Place the egg whites the Thermomix bowl with the butterfly attachment in place. Whisk for 4 minutes / 37 degrees / speed 3.5 / MC off. You should be able to turn the bowl upside down without the eggs coming out. Now set the Thermomix to 4 minutes / speed 3 / MC off and while it is mixing, slowly add the sugar through the hole, 1 tablespoon at a time. The meringue mixture should be smooth and glossy.
Transfer the meringue mixture to a piping bag with a large piping nozzle - I recommend using the Wilton 1M.
Pipe the meringue onto the cupcakes.
Bake in a hot oven (200C / 400F) for around 5 minutes, until the meringue is golden brown.