Preheat the oven to 325°F (160°C). Line two baking sheets with parchment paper.
In a large bowl, whisk together the almond flour, granulated sugar, salt, and lemon zest. Break up any lumps in the almond flour.
In a separate bowl, beat the egg whites with an electric mixer until stiff peaks form.
Add them to the almond flour mixture along with the almond extract.
Gently fold until everything is combined and you get a thick, sticky dough.
Place the powdered sugar in a shallow bowl.
Scoop the dough into about 1 ½ tablespoon (1-ounce) portions and roll into balls. If the dough is too sticky, wet your hands with a little water.
Roll each ball in powdered sugar and arrange on the prepared baking sheets about 2 inches apart.
Bake for 16-18 minutes, until the tops are crackled and the bottoms are just beginning to turn pale golden.
The baked cookies should remain light in color and still feel slightly soft in the center.
Let cool on the baking sheets for 5-10 minutes before transferring to a wire rack to cool completely.
Notes
Blanched almond flour is recommended for this recipe. Using almond meal or unblanched almond flour will result in darker, speckled cookies.
The dough should be soft and sticky but firm enough to hold its shape. If it's too wet, add a little more almond flour, 1 tablespoon at a time. If the dough is too dry or crumbly, add a small amount of beaten egg white.
Coat the cookies well in powdered sugar to highlight the cracks as they bake.
Don’t overbake. The cookies will continue to firm up as they cool, so the centers should still feel slightly soft when you take them out of the oven.