Step 1In a large saucepan, heat 1 tablespoon oil over medium-low heat. Add the white onion and ras el hanout and sweat until the onion is translucent, 6 to 8 minutes. Add the couscous over low heat and stir for 3 minutes, then add the broth. Raise heat to bring to a boil, and cook until the couscous is tender, 15 to 20 minutes. Spread the cooked couscous onto a shallow rimmed pan to cool, stirring occasionally.
Step 2In a large bowl, combine the red and green onions, bell pepper, tarragon, mint, cilantro, parsley, lemon juice, vinegar, garlic and remaining oil along with the couscous, gently mixing with your hands to separate the couscous and fold together the ingredients. Taste and adjust the seasoning as desired.
Step 3Cover and refrigerate for at least 4 hours to give the flavors time to marry. Remove from the refrigerator at least 2 hours before serving to come to room temperature, and stir once more before serving.