In a blender or food processor, add the cilantro, parsley, onion, garlic, salt, pepper, Italian seasoning, red pepper flakes, oil and vinegar. Pulse a few times, until finely minced. Do not over process into a paste.
Pour into a bowl, cover and let stand at least 5 to 10 minutes before serving. If you have time make ahead and let it stand for about 2 hours before serving.