Place the steak in a deep container, and add the lime zest and juice, olive oil, garlic clove, and black pepper to taste. Cover and refrigerate overnight. Preheat grill to high heat (400-500° F). Season steak with salt to taste just before grilling. Grill until your preferred level of doneness (130-140° F for medium rare). Allow the steak to rest before chopping into small pieces. Excluding the tortillas, combine remaining ingredients in a bowl, and stir well to combine. Add the chopped steak, and mix well. Divide the mixture evenly among the tortillas.