Melt butter over medium high heat in an eight inch non-stick skillet. Add vegetables which may need to be cooked, for example, onions, peppers or mushrooms. Cook vegetables for 2 minutes. In a small bowl, beat eggs with water and season with salt and pepper. Pour into pan and stir. Allow eggs to cook for 1 minute and then top with cheese or other toppings. When only a small amount of egg liquid remains, carefully fold omelet in half. Slide onto plate and serve warm.