Cook rice in water as directed on package, omitting margarine and salt.
Meanwhile, cut tofu into small bite-sized cubes; toss with cornstarch. Spray large nonstick skillet with nonstick cooking spray. Heat over medium-high heat until hot. Add tofu; cook 5 to 8 minutes or until golden brown, stirring frequently. Place tofu on plate.
Add bell pepper, onion and pineapple with juice to same skillet. Bring to a boil. Reduce heat; simmer 7 to 10 minutes or until onion is tender and liquid has been reduced.
Add cooked tofu and sweet and sour sauce; stir gently to mix. Cover; cook 1 minute or until bubbly and thickened. Serve over rice.