In a food processor or blender combine the lime juice, oil, garlic, cumin, jalapeno and cilantro leaves and process until pureed. Alternatively, combine the lime juice and oil in a bowl. Finely chop together the garlic, cumin, jalapeno and cilantro and whisk into the juice and oil mixture. Pour the mixture over the steak and allow to marinate for 30 minutes.
Preheat charcoal grill or stovetop grill pan. Season the steak with salt and pepper. Grill the steak for 2 to 3 minutes per side or until cooked to desired degree of doneness. Transfer the steak to a cutting surface and allow to stand for 5 to 8 minutes. Cut steak across the grain into thin slices or chop into 1/2-inch pieces. Serve immediately with warm tortillas and accompaniments.