Combine first 5 ingredients in a large bowl; set aside.
Beat egg whites with a mixer at high speed until soft peaks form; add flour, beating until stiff peaks form. Fold egg white into egg substitute mixture.
Coat a 6-inch nonstick skillet with cooking spray; place over medium heat until hot. Pour half of egg white mixture into pan, spreading evenly. Cover and cook 5 minutes or until center is set. Layer half each of alfalfa sprouts, tomato, and cheese over half of omelet. Loosen omelet with spatula; fold in half. Slide omelet onto a plate. Repeat procedure with remaining egg white mixture, sprouts, tomato, and cheese. Serve immediately.