Cut round tofu into bite-sized pieces.
Julienne the onion and green onion.
Heat cooking oil in a pan and sauté the onion and green onion.
Add the round tofu and stir-fry together.
Mix soy sauce, Korean chili powder, minced garlic, and water to make the sauce.
Pour the sauce into the pan and simmer over medium-low heat.
When the sauce is reduced, finish with sesame oil and sprinkle with sesame seeds.