In a large bowl, whisk together the egg whites and lemon juice until they are well combined.
Gradually add the confectioner's sugar and continue whisking until the mixture is smooth and creamy. If desired, add a few drops of food coloring and mix until blended.
Using a spatula, spread the royal icing onto the cake or cookies. Let the icing set for about 15 minutes before serving.
Interesting Facts
Royal icing is a type of icing used for decorating cakes and cookies.
Royal icing is made with egg whites and confectioner's sugar.
You can add food coloring to the royal icing to make it any color you want.