In a medium bowl, combine the cubed beef, oyster sauce, soy sauce, fish sauce, sugar, and half of the minced garlic. Toss well to coat every piece of steak, then cover and marinate at room temperature for 15 minutes to let the savory flavors penetrate the meat.

While the beef marinates, prepare the traditional dipping sauce by whisking the fresh lime juice, freshly ground black pepper, and a pinch of salt together in a small bowl until the salt dissolves.

Arrange a bed of crisp butter lettuce leaves, sliced tomatoes, and thin red onion rings on a large serving platter to create a fresh, cool vegetable base for the hot beef.

Heat one tablespoon of vegetable oil in a large wok or heavy skillet over high heat until it begins to shimmer. Add the remaining minced garlic and stir-fry for about 10 seconds until fragrant and lightly golden.

Add the marinated beef to the hot skillet in a single, even layer, leaving behind any excess marinade in the bowl. Sear the beef without moving it for 1 to 2 minutes until a deep brown crust forms on the bottom.

Toss and stir-fry the beef quickly for another 2 to 3 minutes until the meat is browned on all sides but still tender and medium-rare in the center.

Spoon the hot, seared beef and its flavorful pan juices directly over the prepared bed of lettuce, tomatoes, and red onions, then serve immediately alongside steamed jasmine rice and the lime-pepper dipping sauce.