Ingredients

8 ounces (5 to 6 medium) tomatillos, husked and rinsed
Fresh hot green chiles, to taste (roughly 2 serranos or 1 jalapeno), stemmed
5 or 6 sprigs fresh cilantro (thick stems removed), roughly chopped
Scant 1/4 cup finely chopped onion
Salt

Steps:

Preheat a broiler.

Roast the tomatillos and chiles on a baking sheet 4 inches below a very hot broiler until darkly roasted, even blackened in spots, about 5 minutes. Flip them over and roast the other side, 4 to 5 minutes more will give you splotchy-black and blistered tomatillos and chiles. In a blender or food processor, combine the tomatillos and chiles, including all the delicious juice that has run onto the baking sheet. Add the cilantro and 1/4 cup water, blend to a coarse puree, and scrape into a serving dish. Rinse the onion under cold water, then shake to remove the excess moisture. Stir into the salsa and season with salt, usually a generous 1/4 teaspoon.

Source: http://www.foodnetwork.com/recipes/salsa-verde-green-tomatillo-salsa-recipe.html