In a medium bowl, whisk together the low-sodium soy sauce, fresh lemon juice, olive oil, Worcestershire sauce, minced garlic, Italian seasoning, dried rosemary, black pepper, salt, onion powder, and brown sugar until well blended.
Place the tri-tip steak in a large resealable plastic bag or a shallow dish. Pour the marinade over the steak, press out excess air from the bag (or cover the dish), and make sure the steak is evenly coated. Seal the bag or cover the dish.
Refrigerate the steak in the marinade for at least 1 hour and up to 24 hours. If possible, turn the bag or flip the steak once or twice during marinating to redistribute the marinade.
About 20 minutes before cooking, remove the steak from the refrigerator to come closer to room temperature.
Remove the steak from the bag or dish and discard the used marinade. Pat the steak dry with paper towels for a better sear.
Cook the steak by your preferred method (grill, broil, or pan-cook) until it reaches your desired doneness (use an instant-read thermometer if available).
Transfer the cooked tri-tip to a cutting board and let it rest for 5 minutes. Slice against the grain and serve.