Set oven rack about 6 inches from the heat source and preheat the oven's broiler. Line a baking sheet with aluminum foil.

Place Hatch chile peppers cut-side down on the prepared sheet.

Cook under the preheated broiler until the skin of the peppers has blackened and blistered, 5 to 8 minutes. Place blackened peppers into a bowl and tightly seal with plastic wrap. Allow peppers to steam as they cool, about 20 minutes. Remove and discard skins.

Combine Hatch chile peppers, ranch dressing, sour cream, cilantro, jalapeno pepper, lime juice, and salt in a blender; puree. Refrigerate until flavors are intensified, at least 1 hour.