For the cookies:
70 gr egg whites
20 gr confectioner sugar
140 gr ice sugar
80 gr almond powder
80 gr lemon juice
100 gr butter
110 gr sugar
150 gr eggs
10 gr corn starch
Line a baking sheet with baking paper.
Whisk egg whites in the bowl of a stand mixer until whites are foam, beat in white sugar and continue beating until egg whites are glossy, fluffy, and hold soft peaks( this is so called french meringue).
Sift confectioners’ sugar and ground almonds in a separate bowl and slowly fold the almond mixture into the egg whites, stirring slowly with a spatula upside-down, till the powder is incorporated into the white eggs.
Spoon a small amount of batter into a plastic bag with a small corner cut off and pipe a test disk of batter, about 1 1/2 inches in diameter, onto prepared baking sheet. If the disk of batter holds a peak instead of flattening immediately, gently fold the batter a few more times and retest.
When batter is mixed enough to flatten immediately into an even disk, spoon into a pastry bag fitted with a plain round tip. Pipe the batter onto the baking sheet in rounds, leaving space between the disks. Let the piped cookies stand out at room temperature until they form a hard skin on top, about 20-30 min.
Preheat the oven to 120°C
Bake macarons for 20 min.
Let the cool aside before filling them with the lemon curd.
For the lemon curd:
In a pan, bring to boil the lemon juice, 1/3 of sugar and the butter. In a bowl mix together the eggs, the rest of sugar and the cord starch. When the lemon juice boils, pour it on the sugar mixture, stirring quickly with a hand whisk; Transfer the mixture into the pan and boil without stopping stirring until you obtain a thick texture but not to thick as the eggs will burn. (around 3 min after the first boil). Transfer it in a jar and let it cool away!