Begin by placing the parsley, cilantro, red wine vinegar, onion, garlic, salt, oregano, hot pepper flakes, and black pepper into the bowl of a food processor. Use short pulses to combine the ingredients until they are coarsely chopped.

While continuing to pulse, gradually add the olive oil to the mixture. Be careful not to over-process; the goal is to achieve a texture that is finely chopped but retains some texture and body.

Once mixed, transfer the chimichurri into a container and refrigerate it. Allow the sauce to marinate for at least two hours so the flavors can meld together beautifully, enhancing the overall taste.