On a cutting board, pile the parsley, garlic, rosemary and scallions. Chop, tossing the mixture a few times, until everything is fine and combined. Scrape the board and add the chopped mixture to a medium bowl.
Stir in the olive oil, vinegar, lemon zest and juice and chile flakes. Season with salt and pepper; a little salt goes a long way here. Serve over steak or beef meatballs.