Heat the broiler to 500°F and place the tomatoes, jalapeños, serranos, onion and garlic on a large pan under the broiler.
Turn the vegetables every 2 to 3 minutes, until the skins split or blacken if you wish.
Add everything to a powerful blender or food processor and blend until nearly smooth.
Serve immediately if you enjoy it warm, or cool for an hour and serve chilled.
