Beat egg yolks with the 2/3 cup sugar until thick and pale yellow; beat in the milk and orange peel.
Sift flour (don't sift instant-type flour), measure, sift with the salt.
Beat egg whites until soft peaks form; gradually beat in the 2 tablespoons sugar until mixture is glossy.
Fold egg yolk mixture and flour into beaten egg whites.
Spoon batter into preheated waffle baker and bake until lightly browned.