Combine almond meal, caster sugar and baking soda in a large bowl
Stir in the vanilla, lemon zest and juice
In a separate bowl, whisk the egg whites until soft peaks form
Fold egg whites into the rest of the mix, until smooth
Using a medium size ice cream scoop, roll tablespoons of mixture into balls, then toss them into the icing sugar, one at a time
Place the sugar-coated cookie balls onto a cookie tray lined with baking paper, leaving space for the cookies to spread slightly
Bake cookies at 160° for 15 minutes, until very lightly golden
Slide baking paper and cookies onto a cool surface for 10 minutes, before cooling completely on a rack.
Notes
These cookies are not meant to spread a lot. If you want flatter cookies, you can give them a little press down halfway through cooking, or as soon as they come out of the oven.