Cook pasta according to package directions, omitting salt and fat.
Meanwhile, melt 1/2 teaspoon butter in a large nonstick skillet over medium heat. Add onion, and sauté 7 minutes or until lightly browned. Add garlic; sauté 30 seconds. Remove from heat.
Combine eggs, egg whites, and next 3 ingredients in a large bowl; stir well with a whisk. Stir in pasta, onion mixture, and spinach.
Melt 1/2 teaspoon butter in same pan; add egg mixture. Cover and cook 12 minutes or until top is almost set.
Spread pasta sauce to within 1 1/2 inches of edges of frittata; sprinkle with cheese.
Wrap handle of pan with foil. Broil 5 minutes or until golden. Cut into 4 wedges.