the black carbon of a comal, i.e. a griddle for cooking tortillas over the fire (see Molina)
IPAspelling:
komɑːltɬiːlli
Alonso de Molina:
comaltlilli. cisco de comalli. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 24r. col. 2. Thanks to Joe Campbell for providing the transcription.