Rub garlic all over steak, and let stand at room temperature. In small colander or sieve, toss radishes with 1/8 teaspoon salt. Place colander over bowl, cover, and refrigerate. Into small bowl, grate peel from 1 lime and cut lime into quarters; set aside. Stir sour cream into lime peel. Cover bowl and refrigerate. Preheat toaster oven to 300°F.

Wrap tortillas in foil, and heat in toaster oven 15 minutes or until warm and pliable. Heat 12-inch cast iron or other heavy skillet on medium-high until hot. Brush garlic off steak and discard. Squeeze juice from lime quarters all over steak, then sprinkle with ¼ teaspoon salt and ¼ teaspoon freshly ground black pepper to season both sides. Add 1 teaspoon oil to skillet, then add steak. Cook 10 minutes for medium-rare, or until desired doneness, turning over once. Transfer steak to cutting board; reduce heat to medium.

Add remaining 1 teaspoon oil to skillet, and add peppers and onion. Cook 2 to 3 minutes or until onion browns, stirring occasionally. Add 1/4 cup water and cook 5 minutes longer or until vegetables are tender, stirring occasionally.

Cut steak across the grain into thin slices. Cut remaining lime into wedges. Divide steak and vegetables among tortillas; top with lime sour cream. Serve with radish salad and lime wedges.