Can I use those pasteurized egg whites (Just Whites) in Royal Icing for decorated cookies? Do I have to use cream of tartar with it? Making cookies for someone that doesn't like merengue powder and I need to have some detail work on the cookies..... Help!

I always thought you needed the Cream of Tartar until I saw this:
http://www.recipelink.com/ch/2002/october/joccookies1.html

Hmmm... But the Just Whites is a liquid... like Egg Beaters type thing... not powdered.

I've never used the Just Whites - I just assumed they were powdered since they are sold in the baking aisle and not the dairy case. If they are liquid and are just pasturized egg whites they should work great for royal icing. I would add a pinch of cream of tartar to give more volume to the egg whites. Use about 1/8 tsp. to the equivalent of 1 egg white.