Place ¼ cup minced red onion, ¼ cup extra-virgin olive oil, ¼ cup white wine vinegar, 2 minced garlic cloves, 2 teaspoons finely chopped fresh parsley leaves, 1 teaspoon Dijon mustard, 1 teaspoon dried dill, 1 teaspoon kosher salt, and ¼ teaspoon red pepper flakes in a jar.
Seal the jar and shake well to combine and emulsify. (Alternatively, whisk everything together in a bowl.)
