Separate the eggs and use the yolks for other purposes.
Divide the powdered sugar into 2 separate bowls of 125 g each and stir the lemon or orange peel into a serving.
In a measuring beaker, beat the egg whites until they are half stiff and pour in the first portion of powdered sugar. Then stir in the second, flavored portion.
The glaze is ready to be applied. It becomes nice and firm and is snow-white.