Cut the tofu into bite-sized pieces.
Slice the onion, green onion, and Cheongyang pepper.
Add sesame oil to a pot, then stir-fry the green onion and minced garlic.
Add the beef and stir-fry, then add the onion.
When the beef is cooked, pour in water and bring to a boil.
Add the tofu, Cheongyang pepper, soy sauce, and doenjang, and boil.
Adjust the seasoning with salt if needed, and finish.