Place parsley, cilantro, green onion, garlic, olive oil, vinegar, lemon juice, red pepper flakes, salt, and pepper into a food processor* and pulse until combined.
Taste and re-season, if necessary, then serve and enjoy!
*For a more traditional method, simply chop the parsley, cilantro, green onions, and garlic to deserved size, then stir in the remaining ingredients.*Make it thinner or thicker, chunkier or smoother. Throw everything together in the food processor at the same time for a thinner, chunkier sauce. Pulse the herbs, onion, and garlic first, then drizzle in the olive oil for a thicker, smoother sauce.