To make the Ladies Fingers:Whisk eggs whites with a electric whisk, adding a pinch of salt.First whist until just foamy, then add ¼ cup of the Xylitol and keep whisking until very stiff.In a bowl whisk the egg yolks with the rest of the Xylitol and the lemon zest, until they become white and foamy and all the Xylitol has dissolved.Now add the egg whites into the yolks, stirring gently with a spatula, being very careful not to overmix and deflate the mixture.Now add the coconut flour, which you have previously mixed with the whey protein, by slowly passing it through a fine sieve.Very gently mix in the flour, until fully incorporated.The dough should be light and fluffy, but not runny.