1 large head iceberg lettuce, core removed and quartered
In a food processor, combine onion, cilantro, lime juice and vinegar. Turn processor on and stream in oil from the chute. Add salt. When the dressing is smooth, green, emulsified in appearance, turn off processor.
Place quarters of iceberg lettuce on a serving platter or on individual salad plates. Pour dressing over "ice burgs" and serve.