Heat 1 teaspoon oil in a large nonstick skillet over medium-high heat. Add onion and chiles; saute 6 minutes. Sprinkle onion mixture with 1/4 teaspoon salt; stir in lime juice. Remove onion mixture from pan. Add 3/4 teaspoon oil to pan. Sprinkle steak with 1/2 teaspoon salt. Place half of steak in a single layer in pan; cook 2 minutes on each side. Repeat procedure with 3/4 teaspoon oil and remaining steak.
Divide steak and onion mixture evenly down center of each tortilla. Top each taco with 1 tablespoon salsa; roll up.