Heat 1/2 tablespoon oil in heavy large non-stick skillet over medium-high heat. Add onion and chilies and saute until tender, about 10 minutes. Transfer onion mixture to bowl (do not wash skillet). Heat 1 tablespoon oil in same skillet over medium-high heat. Add potatoes and saute until golden brown and tender, about 12 minutes. Return onion mixture to skillet with potatoes and keep warm.
Meanwhile, sprinkle both sides of steak generously with garlic powder, chili powder, salt and pepper. Heat remaining 1/2 tablespoon oil in heavy large skillet over medium-high heat. Add steak and cook until browned on both sides, turning once, about 8 minutes total for medium-rare. Transfer steak to cutting board; let rest 5 minutes.
While steak rests, heat tortillas on griddle or over gas flame until warm, turning frequently with tongs.
Thinly slice steak. Top tortillas with steak and potato mixture; sprinkle with cilantro. Serve passing pico de gallo and/or hot sauce separately.
