Juice and zest of two limes
1 tablespoon olive oil
1 tablespoon chili powder
1 teaspoon cumin
1 teaspoon paprika
2 garlic cloves, minced
1 ½ pounds flank steak
1 ½ teaspoons kosher salt
1 teaspoon freshly ground black pepper
12 large lettuce leaves
Guacamole (optional, for topping)
Sour cream (optional, for topping)
Salsa (optional, for topping)
Combine the lime juice and zest, olive oil, chili powder, cumin, paprika, and garlic in a large resealable plastic bag.
Season the steak on both sides with salt and pepper, and then add it to the bag with the marinade mixture. Refrigerate for 20 to 30 minutes.
Preheat a grill or grill pan over high heat. Grill the steak, turning over once, until it is well seared on each side and medium-rare in the center, about five minutes per side.
Transfer the steak to a cutting board and tent it loosely with foil. Let it rest for 10 minutes before slicing across the grain into slices about ¼-inch thick.
To serve, put the steak slices in the lettuce leaves, and top it with guacamole, sour cream, salsa, or any other desired toppings.