In a small bowl, whisk together the orange juice, lime juice, olive oil, garlic, oregano, chili powder, salt, cumin, pepper, and cayenne.
Place the steak in a 9x13-inch baking dish or a plastic zip-top bag. Cover it with the marinade and turn to coat. Let the steak marinate in the fridge for 1 to 4 hours.
Discard the extra marinade, then season the steak with salt and pepper.
Heat the grill to medium-high heat (400-450°F). Add the steak to the grill and cook for 5 to 8 minutes per side for medium-rare (notes below).
Transfer the steak to a cutting board and let rest for 5 to 10 minutes. Thinly slice the steak against the grain and serve.
