Whisk together lime juice, garlic, sugar, fish sauce and sesame oil in a jug. Place steak in a large snap lock bag. Drizzle with half the dressing. Place in fridge for 15 minutes to develop the flavours, if time allows.
Preheat a chargrill pan or barbecue over high heat. Cook steak for 2-3 minutes each side for medium-rare or until cooked to your liking. Transfer to a plate covered loosely with foil for 5 minutes to rest.
Place lettuce, tomato, cucumber, onion and your choice of herbs in a large bowl. Thinly slice steak across grain and add to salad. Drizzle with remaining dressing and gently toss to combine. Divide salad among bowls, sprinkle with peanuts and chilli, if using, and serve with lime wedges.
The longer you marinate the beef the more flavour it will develop – but 15 minutes will be fine for a mid-week meal.
For a more filling meal add rice vermicelli noodles to the salad or serve with steamed rice of your choice.
Sirloin, eye fillet or porterhouse steak would also be delicious in this recipe.