Grease a bowl of a standing mixer with half the lemon. Put the egg whites in the bowl with the salt. Turn on low speed until the egg whites become frothy. Then increase the speed and add the icing sugar. Whisk until the egg whites have formed soft peaks.
When the icing sugar has done with the egg whites, put the water with the sugar on the heat. Let this boil up to 121ºC.
When the sugar solution is 121ºC, pour it into the egg whites while the machine is running. Allow to rotate until the meringue has reached room temperature. Then put away to cool.