In a food processor, combine the tomatillos, onion, jalapeno, and cilantro; cover and process until smooth. Stir in lime juice and salt and pepper to taste. Set aside.
Heat a grill or grill pan to medium-high. Pat the steak dry with paper towel. With one hand, scoop up 1 teaspoon salt and hold it 6 to 8 inches above the steak. Sprinkle the salt evenly across the steak then flip it over and repeat. Holding the salt above the steak allows for more even spreading and a light, thorough coating.
Place the salted steak on the grill and cook for about 3 minutes on each side or until cooked to desired doneness. Remove the steak from the grill and let rest for 5 minutes. Slice against the grain and serve drizzled with the reserved salsa. Cover and chill any remaining salsa up to 1 week.