Place tomatillos and chiles in medium saucepan; add enough water to cover. Bring to a boil; cook 5 to 8 minutes or until tomatillos are just tender, stirring occasionally. Drain.
Cooking Tip: Also known as arbol chiles, chile de arbol are narrow, curved chiles that are bright red when mature and remain bright red even after drying. Chile de arbol are related to cayenne pepper and are very hot.
Place tomatillo mixture, 1/4 cup cilantro and garlic in food processor or blender container. Cover; process until finely chopped, but not pureed. Season with salt and black pepper, as desired. Set aside.
Meanwhile press 1/4 teaspoon black pepper evenly onto beef Flat Iron Steaks. Heat large nonstick skillet over medium heat until hot. Place steaks in skillet; cook 11 to 14 minutes for medium rare (145°F) to medium (160°F) doneness, turning occasionally.
Carve steaks across the grain into thin slices; season with salt and black pepper, as desired. Spoon tomatillo sauce over steak. Serve in flour tortillas, if desired. Garnish with additional cilantro, if desired.
Nutrition information per serving: 221 Calories; 108 Calories from fat; 12g Total Fat (4 g Saturated Fat; 5 g Monounsaturated Fat;) 7 mg Cholesterol; 67 mg Sodium; 6 g Total Carbohydrate; 1.7 g Dietary Fiber; 22 g Protein; 3 mg Iron; 4.8 mg NE Niacin; 0.4 mg Vitamin B6; 5 mcg Vitamin B12; 7.9 mg Zinc; 32.7 mcg Selenium.
This recipe is an excellent source of Protein, Niacin, Vitamin B6, Vitamin B12, Zinc, and Selenium; and a good source of Iron.