There is speculation that which indigenous people, who lived in the wild vanilla-growing regions in Mesoamerica, were among the first to use wild vanilla in cooking?

... the oldest reports of vanilla usage come from the pre-Columbian Maya. The Maya used vanilla in a beverage made with cacao and other spices.

The Olmeca people on the Gulf Coast of Mexico were perhaps the first to use vanilla as a flavoring in beverages. Before that, vanilla was used as a fragrance in temples and the flowers were placed inside of amulets to protect the wearer from the evil eye.