Preheat the oven to 325°F and line two large baking sheets with parchment paper.
Work the lemon zest into the sugar. In a small bowl, combine the sugar and finely grated lemon zest. Work the zest into the sugar with a spoon, stirring for a few minutes until evenly combined. The sugar will feel like wet sand between your fingertips, and the zest should be fragrant, and fully incorporated into the sugar.
Mix the dry ingredients. Whisk together the almond flour, lemon sugar, and salt in a medium-sized bowl.
Whisk the egg whites. In a large mixing bowl using an electric mixer or the bowl of a stand mixer fitted with a whisk attachment, whisk the egg whites on high speed for (2-4 minutes) or until stiff peaks form. Be careful not to over-whip your egg whites as they may start to clump.
Add the limoncello, almond extract, and almond flour mixture. Using a silicone spatula, fold in the almond extract, limoncello, and half of the almond flour mixture into the egg mixture until combined.
Form the dough. Fold in the other half of the almond flour mixture until fully combined. You can be firm with the spatula making sure to incorporate all of the ingredients. If using a stand mixer, turn the mixer on low speed and add the almond mixture slowly until fully incorporated. The dough will be soft and sticky.
Roll into balls. Add the granulated sugar and powdered sugar into two separate bowls. Using a small cookie scoop or spoon, scoop and roll the dough with clean hands into 1-inch balls or (24 grams) weighed on a food scale. Roll each cookie dough ball into the granulated sugar, and then into the powdered until completely coated. Roll into a ball with your hands again to create a uniform round shape. You may need to dampen your hands while rolling the balls, as the dough is quite sticky.
Bake. Place the dough balls onto the parchment-lined baking sheet about 2 inches apart. Bake for 20-22 minutes, or until the cracks are set and the bottoms are golden brown.
Cool the cookies. Let the cookies rest on the tray for 5 minutes, then transfer to a cooling wire rack.