1.Combine oil and pepper in a shallow dish, add steaks, turn to coat.
2.Heat an oiled chargrill pan (or barbecue or grill) over medium-high heat, cook steaks for 2 minutes each side or until cooked as desired. Remove from pan, cover, rest 5 minutes.
3.Cook tomato clusters in chargrill pan for 3 minutes or until softened. Remove from pan.
4.Toast bread slices in chargrill pan for 30 seconds each side. Spread aïoli onto half the toasted slices, top each with steak, onion relish and watercress, then remaining toasted bread slices. Serve sandwiches with tomato clusters.
Aïoli is garlic mayonnaise, available from the condiment aisle in most supermarkets.Note