Douglas, I was just wondering about using the iron skillet or comal and the tomatoes. I tried a different recipe the other day and used my iron skillet to toast the ancho chilies, tomatoes and serrano peppers it called for. After blending all the ingredients, I used the same skillet to heat and cook the finished sauce. I only thought about it after the fact and wondered if the acidic sauce changed in flavor by using the iron skillet. I am sure our grandmothers used their iron for everything and never worried about the acid in them, so I am sure this question is moot, but I still want to know. I am not a very good cook, even though I try, and last weeks sauce did not turn out very tasty. I am going to give this one a try and hope it comes out better. Thank you for posting this.