Beat egg whites and cream of tartar at high speed of an electric mixer until stiff peaks form. Combine egg yolks and flour in a large bowl; beat until thick and pale. Fold one-third of beaten egg white into egg yolk mixture; fold in remaining egg white. Fold in Cheddar cheese and next 3 ingredients.
Coat a 10-inch ovenproof skillet with cooking spray; add 1 teaspoon margarine. Place over medium heat until margarine melts. Pour half of egg mixture into skillet, smoothing top. Cook 3 to 4 minutes or until browned on bottom. Transfer skillet to oven; bake at 350° for 10 minutes or until puffed and golden. Cut a 1/4-inch-deep slit down center of omelet, and top with half each of tomato, chiles, olives, green onions, and sour cream. Loosen omelet with spatula, and carefully fold in half. Slide omelet onto a serving platter, and cut in half. Repeat procedure with remaining 1 teaspoon margarine, egg mixture, and toppings.