This is a recipe I came up with trying to duplicate my favorite omelet from an old local Seattle restaurant called the Steak and Eggs that closed many years ago. I usually use leftover potatoes from the night before.
Beat eggs with water; season with salt and pepper. Set aside. Spray an 8-inch omelet pan or nonstick skillet with cooking spray. Heat skillet over medium heat.
Add potatoes to skillet. Heat until heated through. (Or microwave until heated through). Set aside.
Pour eggs into skillet. (Eggs should set immediately at edges). With an inverted pancake turner, carefully push cooked portions at edges toward center so uncooked portions can reach hot pan surface, tilting pan and moving cooked portions as necessary.
Spoon potatoes over half of the omelet. Spoon sour cream over the potatoes. Sprinkle green onions over the sour cream. Cook for about 30 seconds more. Slide from pan onto plate.
Top omelet with a dollop of sour cream and green onions if desired.