Heat barbecue to medium high. Rub the steaks with the herb paste and set aside. Set the red pepper, onion and garlic on a double layer of foil. Drizzle with 1 tbsp (15 mL) of the olive oil and balsamic vinegar and sprinkle with 1/8 tsp (0.5 mL) each of salt and pepper. Seal foil tightly into a packet. Set on the grill and cook with the lid closed 8 to 10 min.
Drizzle the steaks with the remaining olive oil. Grill for 2 to 3 min. per side for medium (160°F/71°C on an instant-read thermometer). Season steaks with remaining salt and pepper. Let rest 5 to 10 min.
Meanwhile, mix the chopped arugula into the red pepper and onion mixture to make a warm relish, seasoning to taste. Thinly slice the steak and serve topped with the relish.
No bbq? In a roasting pan, combine the red pepper, onion and garlic with 1 tbsp (15 mL) of olive oil, the vinegar and 1⁄8 tsp (0.5 mL) each salt and pepper. Set the pan in the top third of the oven and broil for 10 to 12 min. or until vegetables are caramelized, stirring occasionally. On the stovetop, sear oiled steaks in an ovenproof skillet over medium-high heat, 1 min. on each side. Transfer the skillet to the oven and broil for 2 to 3 min. per side for medium (160°F/70°C on an instant-read thermometer).