Pre-heat the oven to 350 degrees and line a cookie sheet with parchment paper and set aside.
In a large bowl, whisk together two egg whites until frothy.
Add ¾ cup white sugar and continue to whisk until the eggs are slightly thickened and glossy, about 2 to 3 minutes.
Whisk in ½ teaspoon almond extract (if using), ¼ teaspoon table salt, and lemon zest (if using).
Gradually fold in the almond flour with a spatula a little at a time until a firm dough comes together.
Using a tablespoon, divide the dough into even balls and roll in the powdered sugar. Then arrange on a cookie sheet with at least 1 ½ inches space between the cookies.
Using the bottom of a clean glass, flatten each cookie to about ½ an inch thick or 1½ wide.
Bake for 10 to 12 minutes, rotating the pan halfway through, until cookies are golden brown on the bottom.
Cool on the baking sheet for 5 minutes and then transfer to a cooling wrack to finish cooling.
Store cookies in a airtight container for up to 3 days or freeze them for up to 1 month. They freeze very well!