Wash fresh parsley and cilantro, pat dry, and finely chop along with oregano, red onion, and garlic. Place in a food processor and pulse until combined, retaining some texture.

Add red pepper flakes, olive oil, red wine vinegar, and lemon juice to the herb mixture. Secure the lid and pulse 2–3 times to blend until glossy.

Taste and sprinkle in kosher salt to preference, then blend briefly to combine.

Transfer chimichurri sauce into a clean jar and refrigerate for 1–3 days before serving for best flavor.