By catastrofy from Winnipeg, Manitoba, Canada
You might check the substitutions on this page. http://whatscookingamerica.net/Q-A/CreamTartar.htm
The texture of the cookie may be slightly different though. Cookies made with cream of tartar seem to have a slight sandy, melt in your mouth type texture to me. But there are many sugar recipes out there that do not use crm of tartar so it isn't a requirement for a good sugar cookie.
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