In an electric mixer fitted with a whisk attachment, beat the egg whites on medium speed until soft peaks form.
Slowly add the sifted powder sugar to the egg whites on medium speed. Scrape down bowl as needed. Add lemon juice.
Tip: For thicker royal icing, add more powder sugar. It should be able to hold its shape when piped, similar in consistency to thick toothpaste.
Beat on medium-high speed for 5-8 minutes until mixture thickens, and becomes stiff. Scrape down bowl, and cover with plastic to avoid a skin from forming when not using.
Add food coloring to your royal icings, and have your colors ready to go before you start decorating.
Keep un-used royal icing in refrigerator for up to 5 days covered in an airtight container.
Tip: Bring to room temperature before using again.