1. Marinate the beef. In a medium bowl, whisk the orange juice, lime juice, soy sauce, beer, oil, smoked paprika (if using), and black pepper to combine. Add the beef directly to the bowl and massage the marinade into the meat being sure to cover all the surfaces. Add the onions and gently massage them into the mix ensuring full coverage. Cover the bowl and refrigerate for at least one hour and up to 6 to 8 hours.
2. Pat the steaks dry. Remove the meat from the marinade and pat it dry on all sides until no moisture remains. 
3. Preheat the skillet. Heat a 12-inch cast-iron skillet or another heavy-gauge pan over high heat with a little oil. 
4. Sear the steaks. When the skillet is smoking hot, Immediately and carefully add the flank steak, and do not move the pieces once they hit the pan.  Set a timer for 5 minutes. At this point, you may use a spatula or a weight to press down on the middles of the flank steak as they cook. Cook steaks on the first side for 2 1/2 minutes, or until nicely browned. Flip and continue cooking for another 2 1/2 minutes for a total of 5 minutes or until medium doneness (about 140°F/60°C).
5. Rest the steak and add the extra sizzle before serving. Rest the steaks tented with foil for at least 5 minutes. Slice thinly across the grain while you heat back up the skillet. Add the sliced meat spread out leaving a “hole” in the middle of the skillet add a spoonful of soy sauce to the hot pan and stir a little while it sizzles and serve immediately Enjoy!

*If your flank steak is a lot thicker than the flank steak I’ve used (and is pictured in this post), you may set the timer for 8 minutes and cook steaks for approximately 4 minutes on each side for medium doneness.