Add warm water to a mixing bowl.
Slowly add the meringue powder to the water, about 1 Tbls at a time, and mix with a hand whisk until dissolved. Continue adding the meringue powder until it is all blended into the water.
Whisk in Cream of Tarter.
Add clear vanilla to the mixing bowl and gently whisk.
Pour all of the confectioner's sugar (all at once) into the mixing bowl.
If using a stand mixer, set at its lowest setting and allow to mix for 10 minutes. You may have to stop once to scrape down the sides of the mixing bowl with a silicone spatula.
The royal icing is now ready to divide and prepare for outline and flood fill thickness. Add food color and then ice your cookies.