Clean or wash all of the peppers and tomatillos and remove the husk off of them. Place them all into a flat roasting pan and place on the top rack of your oven and set to broil. You should watch carefully. They should be blackened but not burned to a crisp. Once one side is complete, pull pan out and turn the peppers and tomatillos over to blacken the other side and repeat.
If you're using a Traeger, you can place directly on rack with no pan. You can set your Traeger to either high and grill the tomatillos to blacken them... or you can set your Traeger to Smoke and let them smoke for a couple of hours -this will obviously give you the best result!
While your peppers and tomatillos are blackening, prepare a large bowl with ice water. When the onion, tomatillos and peppers are done, place them directly into the ice water and let chill for at least 10 minutes.
Once they have cooled, using your fingers or a small knife, remove the stems and as much of the blackened skin as possible - discarding the stems and skin. Place the remaining parts into the blender. Depending on how much you're making and how big your blender is, you make need to do this in difference parts.
Puree the tomatillos, peppers and onion for about 10 seconds. Then add the spices and blend for about 2 minutes on high. Pour mixture into a bowl and let chill in the refrigerator for approximately 1 hour. The Salsa is ready to enjoy now but it takes about an hour for the flavors to marry. Stir well.