Preheat your oven to 450 degrees. Place tomatillos, chiles, and garlic on a baking sheet.
Place baking sheet on rack closest to the heating source and bake for 15 minutes, turning the tomatillos once. The tomatillos should be lightly charred.
Put tomatillos, chiles, and garlic in the blender. Add cilantro, raw onion, and lime juice. Season with salt.
Blend until mixture is smooth.
Chill and serve with chips or over tacos.