Prepare all ingredients and wash them thoroughly. Cut the bell pepper and onion into 3/4-inch (2 x 2 cm) cubes.

Marinate the beef with: 1/2 crushed garlic clove, black pepper, salt, 2 tablespoons pineapple juice (30 ml), 1 tablespoon ketchup, 1 tablespoon oyster sauce, and 1 tablespoon vegetable oil. Mix well and let sit for 15 minutes to absorb the flavors.

Heat a pan and add 2 tablespoons vegetable oil. Sauté the remaining crushed garlic until fragrant, then add the marinated beef and stir-fry.

When the beef is just cooked, add the bell pepper and onion. Stir well, season to taste (you can add soy sauce and a pinch of bouillon if desired). Transfer to a plate and garnish with cilantro and green onion.