For the stir-fry:
1 pound firm tofu, drained
3 tablespoons vegetable oil
8 ounces fresh or frozen broccoli florets
1 medium red bell pepper, seeded and thinly sliced
1 tablespoon minced peeled fresh ginger
Toasted sesame seeds, for sprinkling (optional)
Steamed rice, for serving
For the sauce:
1/4 cup water
2 tablespoons chili-garlic paste, such as sambal oelek
1 1/2 tablespoons ketchup
1 tablespoon tamari or soy sauce
1 tablespoon rice vinegar
2 teaspoons cornstarch
1 1/2 teaspoons dry sherry
1 1/2 teaspoons packed dark brown sugar
1/2 teaspoon toasted sesame seed oil
Bring a large saucepan of salted water to a boil over medium-high heat. Meanwhile, line a large plate with a double layer of paper towels. Cut the tofu into 1-inch cubes and place in a single layer on the paper towels; set aside.
Heat the oil in a large nonstick frying pan over medium-high heat until shimmering. Add the tofu in a single layer and season generously with salt. Cook undisturbed until golden-brown on the bottom, 8 to 10 minutes. Meanwhile, add the broccoli to the boiling water and cook until crisp-tender, about 3 minutes. Drain and set the broccoli aside.
Flip the tofu with tongs and cook until a second side is golden-brown, about 5 minutes more. Meanwhile, stir all the sauce ingredients together in a small bowl and set aside. Remove the tofu to a clean plate and set aside.
Add the bell pepper and ginger to the pan and stir fry for 1 minute. Add the broccoli and tofu. Stir the sauce again, making sure the cornstarch is fully dissolved, and add it to the pan. Cook, stirring constantly, until the sauce fully coats the tofu and vegetables and thickens, about 2 minutes more. Sprinkle with sesame seeds, if using, and serve over rice.