Preheat oven to 350 F (180 C).
Line a baking tray with parchment paper.
In a bowl add icing sugar and keep to the side.
In another bowl, mix the almond flour, salt and sugar and lemon zest until well combined.
In a stand mixer with a whisk attachment, whisk egg whites till soft peaks form. This can take 3-4 minutes.
Add in almond extract (or vanilla extract) and give it a quick whisk.
Add the almond flour-sugar mixture to the egg whites and FOLD with a spatula. Do it gently to prevent the egg whites from deflating.
Pick up about 1 tablespoons of the mixture (you can use an ice cream scoop) and roll into a ball in the palm of your hand. If the mixture is sticky, lightly oil your hands.
Drop the balls in the icing sugar bowl to completely cover it. Then place them on the baking tray.
Bake them for 25 minutes or until the top appears cracked and golden.
Transfer to a wire rack and allow them to cool completely.