Combine marinade. In a large glass container big enough to hold the meat, mix together the orange juice, lime juice, sliced onion, minced cilantro and parsley, olive oil, 3 teaspoons salt, smoked paprika, sugar, cumin, oregano, garlic powder, and bay leaves.

Pound steak. Lay steak on a non-wood surface (like a plastic cutting board) and cover with plastic wrap. Beat steak with a meat mallet or hammer until it is 1/2-inch even thickness.

Marinate meat. Place meat in the onion mixture and massage mixture into the meat. Sandwich between two layers of onions. Cover and refrigerate for at least 2 hours but best overnight.

Heat grill. Remove the beef from the fridge and let it sit at room temperature while you heat the grill. Light a gas or charcoal grill and heat to medium-high heat. Trim the spring onions and lay on a baking sheet drizzle a little olive oil over the onions and season with salt and pepper. Warm the tortillas and prepare the remaining garnishes while you wait for the grill to heat.

Grill onions and corn. Lay spring onions and corn in its husks (if using) on the grill. Cook for about 10 minutes or until lightly charred, turning occasionally. Push to the side away from the heat to keep warm. Clean the grill grate.

Grill steak. Lift the beef from the marinade and either leave the onions that are sticking to the meat on or brush them off, either way is fine. Lay the meat on the grill, close the lid and let cook, undisturbed until the meat is lightly charred on the edge and has formed grill marks, about 5-8 minutes. Flip, close the lid again and cook another 5-8 minutes depending on how done you like your steak and how hot the grill is. Use a meat thermometer if you're unsure how to test by feel. For carne asada we like it medium which is about 140°F-150°F.

Slice. Remove onions, corn, and steak from the grill and let beef rest about 5 minutes before slicing. While you wait for the meat to rest, slice the onions and remove the husks and silk from the corn and cut each ear into 3 pieces. Slice the steak against the grain (these lines are easy to see in a flank steak), then cut into bite-sized pieces.

Serve. Serve meat, onions, and corn with warm tortillas and all the garnishes.