Cut the tofu into bite-sized pieces.
Slice the onion, green onion, and spicy green chili.
Heat sesame oil in a pot and stir-fry the onion, green onion, and chili.
Add gochujang, Korean chili powder, soy sauce, and minced garlic, then stir-fry together.
Add the canned tuna after draining some of the oil, and stir-fry with the vegetables.
Pour in water or broth and bring to a boil.
Add the tofu and simmer over medium-low heat for 5 to 10 minutes.
Season with salt and pepper, and garnish with green onion to finish.