What the heck is it? And how can I make it? lol

What one restaurant does down here is...

he grills the tomatillo's (with husks on),
grilled/charred jalapeno peppers (skin them)
grilled onions
garlic cloves
on an open fire grill and chars the skin.
Peel the husks and green skins off the tomatillo's
cut up all the charred veggies to add to salsa and mix with salt and pepper and fresh cilantro.

Depending on taste, you have grilled onions, peppers, and garlic to add to your pureed charred tomatillo's with salt and pepper and fresh cilantro.