Bring a pot of water to a boil; add the tomatillos, jalapenos, onion, and garlic. Simmer for 10 to 15 minutes, until the tomatillos are semi-soft. Drain and cool slightly, then put them( all the ingredientsthat have been simmering) in a blender. Add the cilantro, lime juice, and cumin. Puree for a few seconds to blend, and then pour in about a 1/4 cup of water and process to a coarse puree; taste and season with a generous(this is key!) pinch of salt. Makes about 2 cups.