Beat the egg whites with a little sugar. Gradually pour in the rest of the sugar until small tips can be pulled out of the mass and stay there. Squeeze the lemon. Add the juice to the egg whites and stir in well.
Equip a disposable piping bag with a star nozzle. Brush the inside of the piping bag with red food coloring and pour in the meringue mixture. Sprinkle hearts made of egg whites on a baking sheet lined with baking paper and place in the oven for 1 hour. Then let cool down completely.