Who was the first "Iron Chef" on Food Network?

When "Iron Chef America" first came on Food Network, it featured the "Battle of the Masters": three American Iron Chefs (Bobby Flay, Mario Batali, and Wolfgang Puck) competing against two Japanese Iron Chefs (Hiroyuki Sakai, who was crowned "King of the Iron Chefs" at the end of the original Japanese series, and Masaharu Morimoto). So all five of these people could be said to be the first Iron Chefs on Food Network, although the first match was Bobby Flay versus Hiroyuki Sakai (Flay won, BTW).

After these initial four episodes, Puck and Sakai never again appeared as Iron Chefs in the Food Network series, but Flay, Batali and Morimoto continued to be Iron Chefs on the Food Network series.

https://en.wikipedia.org/wiki/List_of_Iron_Chef_America_episodes

The first "specials" of Iron Chef America were taped in Los Angeles, which was convenient to Chef Puck. Once the network picked up the regular series, taping was moved to New York City, which was not at all convenient to Chef Puck who withdrew.

https://en.wikipedia.org/wiki/Iron_Chef_America