1/2 tablespoon sesame seeds, plus more for topping
2 sliced scallions, white and green parts
Combine the soy sauce, 2 tablespoons water, brown sugar, sesame oil and red pepper flakes in a small bowl.
Heat a large deep nonstick skillet over high heat, spray with oil and add the ground beef. Cook, breaking the meat up with a wooden spoon until cooked through, about 5 minutes. Add the onion, garlic and ginger and cook 1 minute. Pour the sauce over the beef, cover and simmer on low heat 10 minutes.
To assemble the bowls, place 3/4 cup rice in each bowl, top with scant 2/3 cup beef, cucumbers, Gochujong, sesame seeds and scallions.