Place the cubed tofu in a bowl. Add 1 tablespoon oil, 2 tablespoons soy sauce, the garlic powder, ground ginger, and 2 teaspoons cornstarch. Toss gently to coat evenly.
Meanwhile, in a small saucepan over medium heat, combine 1/4 cup soy sauce, 1/3 cup water, the brown sugar, rice vinegar, and toasted sesame oil.
Lower the skillet heat and add the thickened sauce. Toss the tofu gently to coat and heat for an additional 2 minutes.