In a bowl, whisk together lightly eggs and water. Over medium-high heat, melt butter in skillet. Pour egg mixture in the pan. Tilt the pan unil the bottom surface is completely covered with egg. Lift up the cooked portion of the egg to allow uncooked egg to run to the bottom of the pan.
Continue cooking until the top of the egg is no longer wet in appearance and bottom of omelet is light golden brown. Remove pan from heat and immediately fill 1/2 of omelet with cheese and/or vegetables of your choice.
Fold the omelet to cover filling, slide onto serving plate. Garnish as desired.
TIP: add a small amount of water to make the omelet light and fluffy.