This is one of those great basic recipes that can be varied in many ways and that goes with all kinds of Oaxacan dishes from stuffed poblano chiles to roasted meats. I’ve had versions enlivened with different chiles (dried or fresh). It also works a great transformation on a simple chicken broth (see Caldo de Pollo).
In Oaxaca sauces of this kind work perfectly year round. In the U.S., I would make it only in the months when the local farm tomatoes