Sift the almond flour with icing sugar. Add the lemon or orange zest. Stir to combine
In a grease-free mixing bowl, add egg white and a pinch of salt and beat with a hand mixer until it is foamy and then add the lemon juice, sugar and almond extract and continue to beat until you get a firm peak
Add the egg white into the almond flour mixture and fold to combine into a wet paste. Dust your work surface lightly with some corn starch. Put the dough paste on top and coat the dough as needed to prevent sticking. Roll into a log. Use a sharp knife to cut diagonally, about 3/4 inch thick
Coat the cut cookies generously with more icing sugar and place on a baking sheet lined with parchment paper. Let them stand for at least 30 minutes to 1 hour. The idea is to "dry out" the surface of the dough a little bit to create the cracks later. Then use your fingers to shape the dough into an oval with more pointy ends and then flatten them slightly with your fingers to encourage to create the "cracks" on top
Baking:
Bake in a preheated oven at 300 F (for a conventional oven) for 20 minutes. If you have a convection oven, lower the temperature by 20 F or 15 C. These are very soft cookies. Let them sit for 10 minutes on the pan before moving to a cooling rack
Storing:
Once the cookies have cooled down completely, transfer them to an air-tight container. They can be kept at room temperature for about 3-4 days
Serve:
They are best served the next day if you can wait. It has a nice soft and chewy texture I can't get over with!