Preheat oven to 350°F. Line a baking sheet with parchment paper.
In a large mixing bowl, whisk together the almond flour and ¾ cup powdered sweetener.
Add the egg whites, lemon zest, lemon juice, and yellow food coloring (if using). Mix with a rubber spatula until a smooth dough forms.
Using a small cookie scoop, portion out the dough and roll each piece into a ball with your hands.
Roll each ball in the reserved ¼ cup of powdered sweetener until fully coated.
Place coated balls on the prepared baking sheet. Use a spatula, flat knife, or the bottom of a glass to flatten each ball into a round cookie shape.
Bake at 350°F for 12–15 minutes, until edges are lightly golden brown and cookies are fragrant.
Remove from oven and allow to cool completely on the baking sheet before transferring. Cookies firm up as they cool. Dust with extra powdered sweetener if desired.