Classic Chimichurri Sauce

Ingredients (7)

• 1 cup packed fresh flat-leaf parsley leaves (leaves from 1 large bunch, about 1.2 ounces—a few small stems are ok)
• 4 medium cloves garlic, peeled
• 1/2 cup extra-virgin olive oil
• 1/4 cup red wine vinegar
• 1/2 teaspoon fine sea salt, to taste
• 1/2 teaspoon red pepper flakes, to taste
• 1/2 cup finely chopped red onion (about 1/2 small)