1. In a small bowl, combine egg, egg white and water, using a fork.
2. In a nonstick skillet over medium heat, cook the egg mixture in canola oil, lifting the edges of the omelet and tilting the pan to allow any uncooked portions to flow to the bottom of the pan.
3. When fully cooked, arrange tomato and cheese on one side of the omelet, folding it in half to cover fillings. To serve, turn omelet out onto a plate. Makes 1 servings.