In a ziptop bag, combine orange juice, lime juice, olive oil, soy sauce, minced garlic, chili powder, ground cumin, paprika, brown sugar, chopped cilantro, and minced jalapeño. Stir well to combine.
Put the steak in the large sealable bag. Press out the air and seal the bag tightly. Massage the marinade into the meat and refrigerate for at least 2 hours, or overnight if time allows. Don’t go over 12 hours as the meat will become mushy rather than tender.
Preheat the grill and prepare it for direct heat cooking over high heat. Clean and lightly oil the grill grates. Remove the steak from the marinade, shaking off the excess. Pat the steak dry with paper towels, and season with salt and pepper and sugar if using.