Lightly coat a 2-quart square baking dish with cooking spray; set aside.
For omelet, in a medium mixing bowl beat egg yolks, onion powder, salt, and 1/8 teaspoon black pepper with an electric mixer on medium speed about 4 minutes or until thick and lemon colored; set aside.
Wash and dry beaters thoroughly. In a large mixing bowl beat egg whites until soft peaks form (tips curl). Gently fold yolk mixture into beaten egg whites. Spread egg mixture evenly in the prepared baking dish.
Bake in a 350 degree F oven for 22 to 25 minutes or until a knife inserted near the center comes out clean.
Meanwhile, for sauce, in a medium saucepan combine undrained tomatoes, zucchini, and remaining 1/8 teaspoon black 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 until desired consistency.
To serve, cut the omelet into quarters. Spoon the sauce over omelet. Makes 4 servings.