In a small bowl, mix fajita seasoning, ancho chile, cumin, cinnamon and red pepper flakes.
Rub steak with olive oil. Sprinkle spice mixture over steak and rub well.
Grill 10 to 12 minutes over high heat, turning once for medium rare, or to desired degree of doneness (steak will be very chewy if cooked past medium). Or, broil 4 to 6 inches from heat following grill instructions.
Remove steak to cutting board and cover loosely with foil. Let rest 5 minutes. Slice thinly into angled slices across the grain.
Serve with tortillas and any condiments you choose.