Heat oil in large skillet over medium-high heat. Add onions and cook 20 to 30 minutes until caramelized, stirring often. Lower heat if necessary. Meanwhile, combine molasses, barbecue sauce, broth and mustard in small bowl. Add molasses mixture to skillet after onions are caramelized; stirring to combine.
Preheat oven to 325°F. Coat shallow roasting pan with nonstick cooking spray. Season both sides of brisket with salt and pepper. Place brisket into prepared pan, fat-side up. Top brisket with onion mixture. Cover tightly with aluminum foil. Braise in 325°F oven 2-1/2 to 3 hours or until brisket is fork-tender.
Remove brisket from roasting pan; keep warm. Trim fat; carve diagonally across the grain into thin slices. Season with salt and pepper, as desired. Serve with caramelized onions mixture. Garnish with pomegranate arils.
Nutrition information per serving: 317 Calories; 76.5 kcal Calories from fat; 8.5 g Total Fat; 2.6 g Saturated Fat; 0 g Trans Fat; 0.5 g Polyunsaturated Fat; 4.3 g Monounsaturated Fat; 96.5 mg Cholesterol; 638 mg Sodium; 23 g Total Carbohydrate; 2.1 g Dietary Fiber; 35 g Protein; 3.8 mg Iron; 464 mg Potassium; 5.1 mg NE Niacin; 0.5 mg Vitamin B6; 2.4 mcg Vitamin B12; 8.2 mg Zinc; 35.4 mcg Selenium; 134.3 mg Choline;