Cream the butter and caster sugar in a mixing bowl until pale in color. You can use a wooden spoon or a handheld mixer.
Add in the egg yolk, lemon juice, and lemon zest. Beat again and mix well.
Fold in the plain flour, cornstarch, and ground almonds. Stir until all is combined and it comes to a dough. Refrigerate for about 30-60 minutes.
Preheat the oven to 180℃/ 356℉ at gas mark 4 when ready to bake the cookies.
Line a few baking sheets with parchment paper/ greaseproof paper.
Take a small piece of the dough or about the size of a cherry tomato, and roll it into a small ball. Then place the dough ball onto the lined baking sheet. Repeat until all the dough is finished. Make sure you leave enough space between the dough balls.
Bake them for about 25 minutes until they are golden in color and firm to the touch.
Once you take the cookies out of the oven, leave them on the sheet for a few minutes before transferring them onto a cooling rack.
Notes
You can prepare the dough and keep it in the fridge for up to 72 hours before cooking.
You can always shape the dough into a giant sausage and cut it into thick slices. So you can save time.
Nutritional info in this recipe is only estimate using online calculator. You should refer to it as a guide only. Please verify with your own data if you seek an accurate info.