Start your Spark and set it to 700°F.
Remove the husks from the tomatillos and wash well. Cut the onion in half. Remove the stems from the chiles.
Place the tomatillos, chiles, and onion onto the grill and roast them until lightly blackened.
Remove from the grill and transfer to a food processor along with the garlic, half a bunch of cilantro, lime juice, a drizzle of olive oil, and the salt. Blend until smooth.
Chop the other half of the onion and the other half of the cilantro.
Transfer the salsa to a bowl and stir in the chopped onion & cilantro. Serve with tortilla chips for dipping.