In a mixing bowl, combine soy sauce, brown sugar, sesame oil, garlic, ginger, gochujang, green onions, and black pepper. Add the sliced beef and mix well. Marinate for at least 30 minutes.

Preheat the grill or a skillet over medium-high heat. Cook the marinated beef for about 5-7 minutes, or until fully cooked, stirring occasionally.

In a bowl, place a serving of cooked rice. Top with the cooked beef, carrots, bell pepper, and sautéed spinach. Garnish with sesame seeds.