separate egg and pre-heat oven to 200°C static.

add lemon zest, 20g erythritol and stevia to egg yolk and whisk until pale and frothy.

add lemon juice drops to egg white and whisk until stiff, then add 10g erythritol and continue to whisk until you have a very stiff meringue.

in a separate bowl, sift flours and give them a good stir.

fold ½ meringue very gently into egg yolk mixture, add sifted flours 1 tablespoon at a time, folding gently so as not to deflate the mix, then incorporate the remaining ½ meringue.

at this point you should end up with a very light and foamy mixture.

spoon onto a lined baking tray, forming 4 equal, oblong shapes (the mixture should not spread itself out at this point, if it does it is too liquid and airless - I'm afraid you'll have to start all over) bake 8-9 minutes until golden and edges start to brown.

the biscuits will harden once completely cold.