Cook chopped potato in a saucepan in boiling water to cover 10 to 12 minutes or until tender.
Coat a large nonstick skillet with cooking spray; place over medium-high heat until hot.
Add potato, tomato, and next 3 ingredients; saute until onion is tender.
Pour egg substitute over vegetable mixture.
Cover skillet; cook over medium-low heat 15 minutes or until set.
Sprinkle with cheese.
Cover; cook 2 minutes or until cheese melts.
Cut into 6 wedges, and serve immediately.
Garnish with green onions, if desired.