In a medium bowl, whisk together ⅓ cup oil, soy sauce, vinegar, Worcestershire sauce, lime zest, lime juice, pepper, garlic powder, and coriander.
In a shallow dish, place steak. Pour mixture over meat, turning to coat. Cover, and refrigerate for 6 hours or overnight.
Heat a large cast-iron skillet over medium-high heat. Add remaining 3 tablespoons oil to pan, and heat until hot. Add steak, and cook 6 to 8 minutes per side, until a meat thermometer inserted in thickest portion registers 130 to 135 degrees for medium rare, or to desired degree of doneness.
Remove from heat, and transfer to a serving platter. Let meat rest for at least 5 minutes before cutting across the grain into thin strips. Serve warm. Garnish with cilantro, if desired.
Recipe by Victoria at https://victoriamag.com/marinated-flank-steak-recipe/