Marinade the steak: Whisk together the marinade ingredients in a large bowl or shake in a plastic bag. Add the steak and turn to coat. Refrigerate for at least 2 hours (or up to 4).
1/4 cup olive oil, 1/4 cup fresh squeezed orange juice, 2 Tablespoons lime juice, 1/4 cup finely chopped cilantro, 4 cloves garlic, 2 teaspoons chili powder, 2 teaspoons smoked paprika, 1 teaspoon cumin, 1 teaspoon kosher salt, 2 pounds flank steak
Grill the steak: Grease the grill grates and preheat to medium-high heat (400-450°F). Grill for 6-8 minutes on each side (depending on thickness), until the internal temperature reaches 135°F for medium-rare.
Cut the steak: Remove the steak to a clean cutting board and rest for 10 minutes to allow the juices to reabsorb. Use a sharp knife to cube into bite-sized pieces.
Prep the toppings: While the steak is resting, chop and prep your desired toppings. Throw the tortillas on the grill for 1-2 minutes to warm or heat in the microwave or oven so they're warm and pliable.
1/2 cup finely chopped cilantro, 1/2 medium white onion, 10 Corn Tortillas
Serve: Add a spoonful of steak to the warm tortillas. Top with onion, cilantro, cotija cheese, other optional toppings, and a squeeze of lime juice.