Spray a 2-quart square baking dish with nonstick spray coating; set aside. For omelet, beat egg yolks, onion powder, salt, and 1/8 teaspoon pepper about 4 minutes or until thick and lemon colored; set aside. Beat egg whites until soft peaks form (tips fold over); fold into egg yolks.
Spread egg mixture evenly into prepared dish. Bake in a 350 degrees F. oven for 22 to 25 minutes or until a knife inserted near the center comes out clean.
Meanwhile combine undrained tomatoes, zucchini, and 1/8 teaspoon pepper. Bring to boiling; reduce heat. Cover and simmer about 5 minutes or until zucchini is tender. Simmer, uncovered, for 10 to 12 minutes more or to desired consistency. To serve, cut omelet into quarters; top with sauce. Makes 4 servings.