In a blender or food processor, blend the cilantro, lime juice, and green onion until smooth. Season to taste with salt and pepper. Add the olive oil in a thin stream, blending well.
Adjust the seasonings and use immediately or chill until ready to serve.
Notes
Store leftovers covered in the refrigerator for up to 4 days. Nutritional values are approximate and based on 1 tablespoon.Turn up the heat: you may want to turn up the heat and add a chopped jalapeño to the processor when you're blending the other fresh ingredients.