Coat a medium nonstick skillet with cooking spray; heat over medium heat.
In a medium bowl, whisk together eggs, egg whites, scallions, salt and pepper until blended. Add egg mixture to skillet; cook, gently turning mixture with a heat proof spatula or wooden spoon, until eggs start to set, about 2 minutes.
Stir in tomatoes and cheese; cook over low heat, gently stirring, just until eggs set, about 1 minute more (there should still be some creamy pieces of cheese). Yields about 3/4 cup per serving.