Heat oven to 325°F.
Put egg yolks, water, salt, pepper, cottage cheese, onion, and parsley into blender container.
Cover; blend at high speed until smooth.
Beat egg whites in large bowl with electric mixer untrL stiff but not dry.
Gently fold in egg yolk mixture.
Heat butter in skillet with heatproof handle until bubbly but not browned.
Add egg mixture.
Cook over low heat 4 to 5 minutes, or until omelet is puffy and underside is golden.
Put skillet in oven.
Bake 10 to 15 minutes, or until omelet is dry and lightly browned on top.
Loosen edges with spatula; slip gently onto warm serving plate.