If you're using whole blanched almonds, place them in a food processor and pulse until finely ground. If you’re using almond flour, you can skip this step.
In a large mixing bowl, combine the ground almonds (or almond flour), sugar, and lemon zest if using. Stir these ingredients together until evenly mixed.
In another bowl, whisk the egg whites until soft peaks form.
Gently fold the whipped egg whites into the almond mixture. Be careful not to deflate the egg whites; the dough will be somewhat sticky.
Using a cookie scoop or spoon, portion out the dough and shape it into balls, about the size of a walnut. Roll each ball in sugar before placing it on a parchment-lined baking sheet.
Preheat your oven to 170°C (340°F) and bake the cookies for about 15-20 minutes, or until they are lightly golden and have developed a crackly top.
Once baked, allow the cookies to cool on the baking sheet for a few minutes before transferring them to a wire rack.
