Raise oven rack to the highest shelf. Turn on broiler. Peel papery covers off of Tomatillos. Place the Tomatillos and Jalapeno on a half sheet tray and broil for 5 min. –
Or until they blister and start cracking. Then turn them over and roast the other side for another 3 minutes.
Transfer Tomatillo to the blender with half of the Jalapeno, cilantro, olive oil, salt, pepper, and lime juice. Pulse the blender and add the water one tablespoon at a time until you reach the desired consistency.
Stir in minced onion and season to your preference with more salt and pepper.