In a large, heavy heatproof pan, spread the onion, garlic, jalapenos, and tomatoes. Drizzle olive oil over all. Place pan under the broiler and cook until tomatoes are charred, about 8 minutes.
Remove and cool to room temperature. Place mixture in a blender or food processor. Add lime juice, cumin, cilantro and water. Process until well combined and slightly chunky, but not completely liquified. Season to taste with salt and pepper.
Makes 3 cups. Nutritional value for 1/4 cup serving.