Combine Pickled Vegetables ingredients in medium bowl; tossing gently to combine. Set aside for 30 minutes, stirring occasionally. Squeeze vegetables dry; place vegetables in large mixing bowl. Combine Brine ingredients in medium sauce pan; bring to a boil over medium heat. Carefully pour hot brine over vegetables, making sure to cover completely. Refrigerate until cold.
Filet beef Flat Iron Steak to 1/4 to 1/3 inches thick. Slice beef pieces in half lengthwise; then into 2-inch squares. Combine all Marinade ingredients but onion in food processor base; process until smooth. Place beef, marinade and onion in food-safe plastic bag; turn steak to coat. Close bag securely and marinate in refrigerator for 30 minutes to 2 hours.
Combine Dipping Sauce ingredients in small bowl; mix until thoroughly combined. Cover and set aside.
Soak 4 bamboo skewers in water for 10 minutes; drain. Place two to three slices of onion in center of each piece of beef; roll tightly into a cylinder. Thread beef rolls onto skewers, leaving room between each roll. Place skewers on preheated gas grill, covered, 7 to 10 minutes for medium rare (145°F) to medium (160°F) doneness, turning occasionally. Keep warm.
Drain Pickled Vegetables; discard liquid and arrange on serving platter. Top with beef rolls. Serve with Dipping Sauce. Garnish with mint, cilantro, garlic, and peanuts, sesame seeds and line, as desired.
Nutrition information per serving: 475 Calories; 117 kcal Calories from fat; 13 g Total Fat; 4.6 g Saturated Fat; 0.4 g Trans Fat; 0.9 g Polyunsaturated Fat; 4.9 g Monounsaturated Fat; 72 mg Cholesterol; 1357 mg Sodium; 68 g Total Carbohydrate; 3.5 g Dietary Fiber; 26 g Protein; 3.5 mg Iron; 815 mg Potassium; 4 mg Niacin; 0.5 mg Vitamin B6; 5.1 mcg Vitamin B12; 8.2 mg Zinc; 34.7 mcg Selenium; 108.5 mg Choline;