Heat oven to 325°F.
In medium bowl, beat egg whites, water and salt with electric mixer on high speed until stiff but not dry. In small bowl, beat egg yolks and pepper on high speed about 3 minutes or until very thick and lemon colored. Fold egg yolks into egg whites.
In 10-inch ovenproof skillet, melt butter over medium heat. As butter melts, tilt skillet to coat bottom. Pour egg mixture into skillet. Gently level surface; reduce heat to low. Cook about 5 minutes or until puffy and bottom is light brown. Carefully lift omelet at edge to see color.
Bake uncovered 12 to 15 minutes or until knife inserted in center comes out clean.
Tilt skillet and slip pancake turner or metal spatula under omelet to loosen. Fold omelet in half, being careful not to break it. Slip onto warm serving plate. Serve with salsa or tomato pasta sauce.