Finely chop 1 cup fresh parsley
Finely chop 1/4 cup fresh oregano (or use 1–2 tbsp dried oregano)
Mince 2–4 garlic cloves
Finely chop 1 small red onion (optional)
Finely chop 1–2 jalapeños or serrano peppers (to taste)
Add 1/2 tsp kosher salt (to taste)
Add 1/2 tsp freshly ground black pepper
Add 1 tsp dried oregano (optional, if using fresh only)
Add 1/2 cup red wine vinegar (or 1/3 cup plus more to taste)
Add 1/2 cup extra-virgin olive oil
Mix thoroughly until well combined
Taste and adjust salt, pepper, vinegar, and oil
Rest 15–30 minutes before serving (optional but recommended)