Prep your pan and oven. Preheat the oven to 325°F (165°C). Line a baking sheet with parchment paper. This helps prevent sticking and promotes even browning.

Cream the butter and sweetener. In a mixing bowl, beat the softened butter with the granular sweetener for 1–2 minutes until light and fluffy. This step is key for that tender shortbread texture.

Add flavor boosters. Mix in the egg yolk, vanilla, lemon zest, and lemon juice. If using almond extract, add it here. Beat until smooth and well combined.

Incorporate the dry ingredients. Add almond flour and salt. Stir or beat on low just until the dough comes together. The dough should be soft but not sticky; if it’s too loose, let it rest 5 minutes so the almond flour hydrates.

Choose your shaping method. For round cookies, scoop 1 tablespoon portions and roll into balls, then flatten to 1/4–1/3 inch thickness. For slice-and-bake, roll the dough into a log (about 1.5 inches diameter), wrap, and chill 30–45 minutes, then slice into rounds.

Bake. Arrange cookies 2 inches apart on the lined sheet. Bake for 10–13 minutes, until edges are lightly golden. Avoid overbaking; they firm up as they cool.

Cool completely. Let the cookies rest on the baking sheet for 10 minutes, then move to a rack. They’re fragile when hot, so handle gently.

Optional lemon glaze. Stir powdered erythritol with lemon juice and a pinch of salt until smooth. Drizzle over cooled cookies. Let the glaze set before storing.