Ingredients
1/2 cup olive oil, plus more for grilling
1 1/2 cups fresh parsley
2 tablespoons fresh oregano
4 teaspoons red-wine vinegar
3 garlic cloves, minced
Salt
1 large red onion, cut into 1/2-inch slices
1 1/4 pounds ground beef chuck (80% lean), formed into four 1-inch-thick patties
4 hamburger buns
Sliced tomato, for serving
Baby arugula or other greens, for serving
Preparation
Heat grill or grill pan to medium-high. Clean and lightly oil hot grill. Meanwhile, in a food processor, combine oil, herbs, vinegar, garlic, and 1 teaspoon salt. Pulse until finely chopped.
Season sliced onions with salt. Grill, turning frequently, until charred and tender, 10 to 14 minutes. Brush with chimichurri sauce and cook 1 minute more, flipping once. Transfer onions to a plate. Season patties with salt. Grill 3 1/2 minutes per side for medium-rare. Serve burgers on buns with onions, tomato, and arugula; top with chimichurri sauce.
