Whisk the Marinade: In a medium bowl, combine soy sauce, brown sugar, sesame oil, minced garlic, grated ginger, and black pepper. Whisk until sugar dissolves.

Marinate the Beef: Place the beef ribeye into the marinade, ensuring each piece is coated. Cover and refrigerate for at least 30 minutes.

Sauté the Onions: Heat vegetable oil in a pan. Sauté onions for 3-4 minutes until translucent.

Cook the Beef: Add marinated beef to the pan. Cook for 5-7 minutes, stirring, until browned and cooked through.

Prepare the Gochujang Sauce: Mix gochujang with rice vinegar in a small bowl. Add water if needed for smoothness.

Assemble Your Dish: Plate steamed rice, top with kimchi and cooked beef mixture, and drizzle with gochujang sauce.

Garnish and Serve: Finish with toasted sesame seeds and chopped green onions. Serve immediately.