Cut Anaheim and onion into chunks. Heat cast iron skillet over high heat. Add olive oil. Add tomatillos, Anaheim, onion and garlic and roast until charred and onions are crunch tender. Add to blender along with rest of ingredients, except lime juice. Blend until smooth, adding lime juice at end and more water as needed. Taste and adjust seasonings.
Notes
I start with these measurements. At the end I taste and adjust...since peppers and tomatillos vary in size, adjusting seasonings and adding more water at the end may be necessary. Also, a sprinkle of sugar helps cut the tartness if your tomatillos are not ripe enough.