1/2 cup plus 2 tbsp balsamic vinegar
3/4 cup plus 3 tablespoons olive oil
4 cloves garlic, coarsely chopped
2 tbsp coarsely chopped rosemary leaves
1 (1-1/2 to 1-3/4) beef flank steak
Salt and freshly ground black pepper
2 cups arugula
1 pound cherry tomatoes, halved
1/2 small red onion, thinly sliced
1 (4-ounce) piece Parmesan cheese
1. Whisk together 1/2 cup of the vinegar, 3/4 cup of the oil, the garlic and rosemary in a large dish (or use a thick, ziplock plastic bag). Add the steak and turn to coat. Cover and let marinate the refrigerator for at least 4 hrs and up to 8 hours, turning every 2 hours.
2. Heat the grill to high.
3. Remove the steak from the marinade and season with salt and pepper. Grill until lightly charred and crusty, 4-5 mins. Turn the steak over, reduce the heat to medium or move to a cooler part of the grill, and grill until medium-rare, 3-4 mins more.
4. Remove the steak to a cutting board and let rest for 5 minutes. Cut into 1/2-inch thick slices agains the grain of the mat.
5. Whisk together the remaining 2 tablespoons vinegar and 3 tablespoons oil in a large bowl and season with salt and pepper. Add the arugula, tomatoes, and onion, and toss to coat. Divide the sliced steak among 4 plates and top with some of the arugula salad. Using a vegetable peeler, shave thin slices of Parmesan over each dish. Serve immediately.
Serves 4; can be doubled for 6-8 (no need to double the marinade).