Make this for our Crispy Pork-Stuffed Anaheim Chiles.
Put tomatillos in a medium saucepan; cover with water by 1 inch. Bring to a boil. Reduce to a simmer. Cook 4 minutes. Drain, reserving 1/2 cup cooking liquid.
Process tomatillos, onion, jalapenos, cilantro, salt, and 1/4 cup liquid in a blender until a slightly chunky sauce forms, adding more liquid as needed.
Refrigerate in an airtight container up to 3 days.