You will need:
100 g / 3 oz sugar, divided
1 lemon, zest and a little juice only
Beat the egg whites super stiff, then mix in half of the sugar until smooth and shiny. Mix in the remaining sugar and lemon zest/juice slowly with a spatula.
Fill the mass into a pastry bag with a star tip and spritz little mounds on cookie sheets that have been lined with parchment paper. If you do not have a pastry bag, you can just form little mounds with two teaspoons.
Bake in a oven with the temperature set at about 100 C / 200 F for about 70 to 100 minutes. The oven door needs to be open just a little bit. The cookies dry more than they bake.
Tip: You can make these in many variations, for a chocolate version, just leave out the lemon zest and switch it out for 1 oz of cocoa powder, for coffee flavor use instant coffee powder, or switch out the lemon zest for orange zest and orange aroma. You could even take two of them and then join them by sticking them together with nutella, jelly or butter cream. Color them with food color or a couple drops of beet juice.. The possibilities are endless!