Prepare the marinade by combining orange juice, lime juice, olive oil, Worcestershire sauce, cilantro, and minced garlic in a small bowl. In another small bowl, whisk together chili powder, sugar, paprika, cumin, onion powder, garlic powder, cayenne pepper, salt, and pepper. (I add about 1 teaspoon salt and 1/4 teaspoon pepper, but add to personal preference.) Add 1 tablespoon of the spice mix to the marinade and whisk to combine.
Using a fork, poke holes about an inch apart all over the steak on one side only. Place the steak in a large freezer bag and pour all but 1/4 cup marinade over the steak. Massage into the steak, seal the bag, and place in the fridge. Refrigerate for at least an hour and up to 8 hours, turning the steak at least once. Remove the steak from the fridge 30 minutes before cooking and let stand at room temperature.
To cook in a skillet
Drain marinade from meat and pat dry with a paper towel. Sprinkle the remaining spices (should be about 1 tablespoon) evenly on both sides of the steak. Pat this mixture over the steak (don't rub it in). Heat a cast iron skillet over medium-high heat with 1 tablespoon olive oil. Cook steak for about 4-5 minutes per side or until steak is medium-rare (130-135 degrees F). Use a meat thermometer for best results. Once cooked, let the meat rest on a cutting board, tented with aluminum foil, for 5-10 minutes. Slice very thinly against the grain into strips.
To cook on a grill or grill pan
Heat grill or grill pan to high heat. Clean and lightly oil the grill grates (or ridges on a grill pan). I do this by pouring a little canola oil over a paper towel, holding it with tongs, and running it along the grates or ridges. Drain the marinade from meat and pat dry with a paper towel. Sprinkle the remaining spices (should be about 1 tablespoon) evenly on both sides of the steak. Pat this mixture over the steak (don't rub it in). Grill the steak, covered, for about 4-5 minutes per side or until steak is medium-rare (130-135 degrees F). Let the meat rest on a cutting board, tented with aluminum foil, for 5-10 minutes. Slice very thinly against the grain into strips.
Vegetables
To cook in a skillet: Slice peppers and onion into thin strips. Wipe down the pan you used to cook the steak in with a paper towel and tongs (doesn't need to be perfectly clean). Add a tablespoon of oil and place over medium-high heat. Add peppers and onions. Season to taste with salt and pepper. Cook, stirring occasionally, until crisp-tender, about 8 minutes.
To cook on a grill or grill pan: Drizzle 2 tablespoons olive oil, salt, and pepper over the 3 full peppers (unsliced) and the sliced onion. Heat a grill to high heat and place the peppers and onions directly over the heat. Turn the peppers every 2 to 3 minutes until they are completely charred, about 10 minutes total. Flip the onion slices after 2-3 minutes and remove after around 6 minutes total or until charred to your liking. Let cool completely and then thinly slice the peppers.
Serve
Fill tortillas with cooked and sliced steak, bell peppers, onions, and any desired toppings such as sour cream, guacamole or sliced avocado, tomatoes or pico, and fresh cilantro and/or lime. Drizzle reserved 1/4 cup marinade over everything. Fold up and enjoy!
Notes
Note 1: If you aren't cooking your own tortillas (TortillaLand® or homemade) warm them up on the grill: Wrap tortillas tightly in foil and grill for 2-3 minutes over medium heat, rotating halfway through.