Cover a baking sheet with aluminum foil and coat with cooking spray. Lay tofu, onions, and peppers on baking sheet and bake 30 to 40 minutes or until soft and lightly brown. Sprinkle with salt and pepper.
Lay tofu on plates. Mix vegetables with Lime Sauce and spoon over tofu. Top with cilantro.
To prepare Lime Sauce: Whisk sugar and cornstarch in a medium pot; whisk in the rest of the ingredients and bring to a boil. Stirring continually, let boil 1 minute, until mixture is thick.