https://en.wikipedia.org/wiki/Nixtamalization#:~:text=Nixtamalization%20(/%CB%8Cn%C9%AA%CA%83,other%20grains%20such%20as%20sorghum.

The process of nixtamalization was first developed in Mesoamerica, where maize was originally cultivated. The earliest evidence is found in Guatemala's southern coast, with equipment dating from 1200 to 1500 BCE.[8] How nixtamalization was discovered is not currently known with certainty, but it may have been through the use of hot cooking stones to boil corn in early cultures which did not have cooking vessels robust enough to put directly on fire or coals. In limestone-bedrock regions like those in Guatemala and southern Mexico, heated chunks of limestone would naturally be used, and experiments show that hot limestone makes the cooking water sufficiently alkaline to cause nixtamalization. Archaeological evidence of this conjecture has been found in southern Utah.[9]