Beat egg whites until foamy. Continue beating and add sifted powdered sugar, one tablespoon at a time, until sugar is completely incorporated. Continue beating for about 10 minutes until the mixture becomes very stiff. Consistency will be somewhat like marshmallow fluff.
Beat in vanilla extract.
Set aside ½ cup of the meringue to use for icing later. Cover it to prevent it from drying out.
Preheat oven to 250 F (120 C).
Set aside ½ cup of the ground nuts or nut flour.
Mix almond extract, cinnamon, lemon juice, optional cardamom, and the remaining 3 ½ cups of the ground nuts or nut flour into the egg white mixture with a wooden spoon or your hands. Consistency should be like a moist cookie dough. If it’s too sticky, add more ground nuts or nut flour, a teaspoon at a time, until proper consistency is reached.
Wrap dough tightly in plastic wrap and let rest in refrigerator for one hour.
Line your work surface with a sheet of parchment paper.
Sprinkle the reserved ½ cup of ground nuts or nut flour on the parchment.
Place the rested dough on top of the nuts. Place a sheet of waxed paper over the dough. Roll out the dough with a rolling pin on top of the waxed paper to ¼ inch thick (½ cm). Remove waxed paper.
Cut out cookies with a star-shaped cutter, leaving about 1 inch between each cookie.
Remove dough between cookies, leaving cutouts on the parchment paper.
Carefully transfer the parchment paper with the cutouts to a baking sheet. The cookies will be very soft, so leaving them on the parchment is an easy way to keep them from becoming deformed while transferring them to the baking sheet.
Re-roll dough as many times as necessary to use it all for cookies. Because there is no flour, the dough will maintain its consistency.
Using a pastry brush or a clean artist paintbrush, ice each cookie with reserved meringue.
Bake in preheated oven for 30 minutes. Meringue will be set, and cookie edges will be just turning a light gold.
Let cool completely on baking sheet.
Using a stand mixer is helpful because of the lengthy beating time.