Heat the oven to 180C/350F and cover a large baking sheet with parchment paper. Use a flat, lined sheet so the delicate cookies release cleanly after cooling.

Whisk the almond flour, salt, allulose or monk fruit sweetener, and lemon zest in a large bowl until evenly blended. Break up any flour or zest clumps now for a smoother, more even crumb.

Beat the room-temperature egg whites in a separate bowl until they form soft peaks, then mix in the lemon extract and optional yellow food coloring. The peaks should bend over at the tip rather than stand stiffly upright.

Fold the dry mixture into the egg whites just until no dry patches remain. The finished dough should feel soft and scoopable, not loose or pourable.

Scoop heaping tablespoons of dough, coat each portion in the sugar free powdered sugar, and arrange them on the prepared baking sheet. Press each ball into a thick disc because the dough will keep its shape in the oven.

Bake for 15 minutes. Remove the cookies when the edges are set and the tops show fine cracks.

Leave the cookies on the baking sheet until completely cool, then add another light dusting of powdered sweetener if the coating has absorbed into the surface. The cookies firm up as they cool, so moving them while warm can cause breakage.