Lay flank steak in a large glass baking dish.

Make the marinade: Whisk soy sauce, oil, vinegar, 4 cloves of garlic, juice of two limes, salt, black pepper, white pepper, garlic powder, chili powder, oregano, cumin, and paprika together in a bowl until well blended; pour over steak, turning to coat both sides. Cover the dish with plastic wrap and marinate in the refrigerator for 1 to 8 hours.

Make the relish: Stir onion, cilantro, and lime juice together in a small bowl. Set aside.

Make the salsa: Preheat the oven to 450 degrees F (230 degrees C). Heat a skillet over medium-high heat. Add chile pods and toast for a few minutes; transfer pods to a bowl of water and soak for 30 minutes.

Place tomatoes, 1 onion, 4 cloves of garlic, and jalapeños onto a baking sheet. Roast in the preheated oven until vegetables are toasted, about 20 minutes.

Transfer vegetables into a blender or food processor. Add soaked chiles, salt, and pepper; puree until smooth.

Remove steak from the marinade and shake off excess. Discard the remaining marinade. Cut the marinated flank steak into cubes or strips. Heat vegetable oil in a large skillet over medium-high heat. Add steak; cook and stir until cooked through and most of the liquid has evaporated.

Warm tortillas in a dry skillet over low heat for about a minute on each side.

Place some steak on each tortilla; top with relish and prepared salsa. Sprinkle with cotija cheese. Garnish with lime wedges and serve.