Yes, Virginia, there is an offical Pizza Margherita recipe. :)
Italians take their pizza very seriously. As they did for wine, they
have established a controlling body (a Denominazione di Origine
Controllata or DOC) for pizza: the Associazone Vera Pizza Napoletana.
This agency produced a document called the Progetto di Norma which
stipulates ingredients and methods required by Associazone members
worldwide to produce "verace pizza napoletana."
The official DOC recipes for pizza dough and for Pizza Margherita can
be found at the following site, but are taken from "Pizza Napoletana!"
by Pamela Sheldon Johns (Ten Speed Press, October 1999).
"Bona Fide Pizza" by Carole Kotkin (The Wine News, Oct-Nov 2002)
(scroll to "Pizza Margherita Extra DOC")
"Souvenir Pie" (Wine Spectator, Nov 15 2001)
official recipe "Pizza Margherita"
Ciao, and grazie!