Slice the onion and green onion.
Cut the tofu into bite-sized pieces.
Add sesame oil to a pan and sauté the onion and green onion.
Add chili powder and stir-fry on low heat.
Pour in water and add minced garlic, then bring to a boil.
Add tuna, then add the soft tofu.
Season with soy sauce and salt, and simmer on low heat.
Transfer to a bowl and top with chopped green onion to finish.