Place tomatillos, serrano peppers and garlic cloves on a baking sheet lined with foil.
Place baking sheet under the broiler and cook until tomatillos are soft and starting to blacked, 7 to 8 minutes. The garlic and serrano peppers should be removed from the tray if starting to blacken too much.
Remove skin from garlic and cut the stems off the serrano peppers.
Using tongs, transfer the tomatillos, serrano peppers and garlic to the bowl of a food processor.
Add cilantro, lime juice and salt, and pulse to puree to a slightly chunky consistency.
Transfer salsa to a serving dish, let cool and serve.