Preheat the oven. Set your oven to 350°F (180°C). Line a baking sheet with parchment paper so the cookies don’t stick and brown evenly.

Mix dry ingredients. In a medium bowl, whisk the almond flour, granulated erythritol, baking soda, and salt until well combined. This prevents clumps and helps the dough mix evenly.

Whisk the wet ingredients. In a separate bowl, whisk the egg, melted butter, lemon zest, lemon juice, and vanilla until smooth. If using lemon extract, add it here.

Combine to form dough. Pour the wet mixture into the dry ingredients and stir with a spatula until a soft dough forms. It should be thick but scoopable, not crumbly.

Rest the dough briefly. Let the dough sit for 3–5 minutes. Almond flour hydrates quickly; this short rest prevents spreading and helps shape the cookies.

Portion the cookies. Use a tablespoon or small cookie scoop to portion 12–14 dough balls onto the baking sheet. Leave about 2 inches between them.

Flatten slightly. Gently press each dough ball to about 1/2 inch thick. Keto cookies don’t spread as much as traditional cookies, so shaping matters.

Bake. Bake for 10–12 minutes, until the edges are just turning golden. The centers should look set but still soft. Do not overbake.

Cool completely. Let the cookies cool on the baking sheet for 10 minutes, then transfer to a rack. They firm up as they cool—be patient.

Make the glaze. In a small bowl, whisk the powdered erythritol with 1 tablespoon lemon juice. Add more juice drop by drop until you reach a drizzleable consistency. Stir in lemon zest if using.

Glaze and set. Once the cookies are fully cool, drizzle the glaze over the tops. Let the glaze set for 15–20 minutes before serving.