Set the oven on broil. Wash and husked the tomatillos, chop in half and put on a baking sheet. Chop the onion and peel the garlic cloves. Add to the baking sheet. Broil for about 8 minutes. Scrape the tomatillos and any juices into a food processor or blender. Puree until thickened and smooth. Add the Cilantro to the food processor and pulse. Season with salt.