Combine marinade ingredients in small bowl. Reserve 2 tablespoons for topping. Place beef Flat Iron Steaks and remaining marinade in food-safe plastic bag; turn steaks to coat. Close bag securely and marinate in refrigerator 15 minutes or up to 2 hours, turning occasionally.
Meanwhile, combine corn, tomato, 2 tablespoons cilantro, salt and reserved 2 tablespoons marinade in medium bowl. Cover and refrigerate.
Cooking Tip: To cook fresh corn on grill, pull back husks from corn, leaving husks attached. Remove and discard corn silk. Bring husks back up around corn; tie in place with kitchen string or strips of corn husk. Soak corn in cold water 30 minutes or up to several hours. Remove corn from water. Place on grid over medium, ash-covered coals; grill, covered, 20 to 30 minutes (over medium heat on preheated gas grill, 15 to 25 minutes) or until tender, turning occasionally. To cook frozen corn on stovetop, heat nonstick skillet over medium heat. Add corn; Cook over medium heat 4 to 6 minutes or until thoroughly heated, stirring occasionally.
Remove steaks from marinade; discard marinade. Place steaks on grid over medium, ash-covered coals. Grill, covered, 10 to 14 minutes (over medium heat on preheated gas grill, 12 to 16 minutes) for medium rare (145°F) to medium (160°F) doneness, turning occasionally.
Remove steaks; keep warm. Place tortillas on grid. Grill, covered, 1 to 2 minutes or until toasted. Turn tortillas over; sprinkle evenly with cheese. Grill 1 to 2 minutes or until toasted and cheese starts to melt.
Carve steak into thin slices. Season with salt, as desired. Top tortillas with equal amounts of steak and corn mixture. Garnish with cilantro, if desired.
Nutrition information per serving: 485 Calories; 207 Calories from fat; 23g Total Fat (11 g Saturated Fat; 7 g Monounsaturated Fat;) 100 mg Cholesterol; 726 mg Sodium; 33 g Total Carbohydrate; 4.4 g Dietary Fiber; 33 g Protein; 2.9 mg Iron; 7.8 mg NE Niacin; 0.4 mg Vitamin B6; 5.3 mcg Vitamin B12; 8.9 mg Zinc; 36.5 mcg Selenium; 106.9 mg Choline.
This recipe is an excellent source of Protein, Niacin, Vitamin B6, Vitamin B12, Zinc, and Selenium; and a good source of Dietary Fiber, Iron, and Choline.