2 teaspoons cornstarch
2 teaspoons sugar
1/4 teaspoon ground ginger
1/4 cup reduced-sodium soy sauce
1 tablespoon cider or white wine vinegar
1 pound beef flank steak, cut into 1/4-in.-thick strips
2 teaspoons canola oil, divided
2 medium green peppers, julienned
Hot cooked rice, optional

Mix first five ingredients until smooth. Add beef; toss to coat.
In a large skillet, heat 1 teaspoon oil over medium-high heat; stir-fry peppers until crisp-tender, 2-3 minutes. Remove from pan.
In same pan, heat remaining oil over medium-high heat; stir-fry beef until browned, 2-3 minutes. Stir in peppers. If desired, serve over rice.