1. Cut the block of tofu in half lengthwise. Put the halves on 4 sheets of paper towels, and cover with another 4 sheets. Cover with a heavy cutting board, or a plate weighted with cans. Change the towels if they become saturated. Weight the tofu for a total of 30 minutes. (Or buy "pressed tofu" and skip this step.)
2. Cut the tofu into 1/2-inch cubes and set aside.
3. Heat the peanut oil in a large nonstick skillet over medium-high heat. Add the bell peppers and cook, stirring occasionally, until browned and tender, about 10 minutes.
4. Add the garlic, ginger, and chile peppers, and cook, stirring, for about 30 seconds. Add the tofu and 2 tablespoons water. Cook, stirring occasionally, until the tofu is hot, about 5 minutes. Add the scallions; stir for about 30 seconds.
5. Turn off the heat, then stir in the soy sauce and sesame oil; garnish with cilantro and serve.