For the lemon curd filling:

Cup of Yum
1. Place a deep saucepan over low heat, add the sugar, eggs, lemon zest and juice, and stir constantly with a spoon.
2. As soon as the mixture starts to evaporate, remove the pot from the heat, continue stirring for a few seconds and return the pot to the heat.
3. Repeat the same process until the mixture starts to thicken.
4. As soon as it thickens, remove the saucepan from the heat, add the butter, and stir until it melts completely.
5. Transfer the mixture to a bowl, wrap the bowl with cling film so it touches the lemon curd and leave aside to cool completely.

For the cookies:

1. In a mixer bowl, place the butter and powdered sugar and beat on medium speed until the butter is fluffy.
2. Pour in the flour and baking powder and knead again until the mixture is homogenized.
3. Remove from the mixing bowl and roll the dough out on a floured counter to a thickness of 4 mm (1/5 of an inch) .
4. With a knife or an egg-shaped cookie cutter, cut the dough into pieces and place them in a baking pan lined with parchment paper.
5. Gather together all the excess dough, roll it out and cut out more cookies. Cut a smaller 2.5 cm/ 1 inch diameter hole in half of the cookies - these will be the top of the cookie sandwich.
6. Bake the cookies in a preheated oven at 175°C/350° F, fan on, for 8 to 10 minutes. Once they are done, take them out of the oven, let them cool well. Cover the cookies that do not have a hole in with a little filling. Then cover each one with a holed cookie and press lightly.
7. Follow the same process for the remaining cookies and serve with powdered sugar.