Cut the beef into bite-sized cubes. Marinate the beef with 2 cloves of minced or sliced garlic (as you prefer), 1 teaspoon soy sauce, 1 teaspoon oyster sauce, 1 teaspoon sugar, 1/2 teaspoon seasoning powder, and black pepper. Let it marinate for about 15 minutes. Prepare the remaining ingredients.

Heat a little oil in a pan and stir-fry the beef until just cooked. Remove the beef and set aside. Sauté a little garlic in the same pan, then stir-fry the bell pepper, adding a bit of seasoning (since the beef is already seasoned). Add the onion and beef back to the pan, stir-fry quickly, taste and adjust seasoning if needed, then add green onions. Done.