Step 1Rinse the tofu block in cold water then cut it in half, then into approximately 1/2-inch slices. Set the tofu aside on paper towels or in a wire-mesh colander to drain.
Step 2Combine the soy sauce, garlic, green onions and optional red pepper or chile powder. Set aside.
Step 3Heat the oil in a large skillet over high heat. Working in two batches, carefully place the tofu into the skillet, making sure each rectangle rests flat on the bottom. (Be careful, because the water in the tofu will make the oil splatter.) You may wish to cover the skillet with a wire-mesh splashguard. Cook the tofu until it is lightly browned on both sides; don't overcook or it will lose its moisture and texture.
Step 4Reduce the heat to low and spoon the soy mixture over each tofu slice. Cover and cook until the tofu is slightly steamed and infused with the seasoning, another 2 or 3 minutes.