Beat egg yolks until thick and lemon-colored; beat in half of the sour cream and the salt.
Fold in the egg whites and ham.
Heat butter in 10-inch skillet; pour in omelet mixture, leveling gently.
Cook over low heat until lightly browned on bottom, about 5 minutes.
Finish cooking in 325° oven until top is golden brown, about 12 minutes.
Finish by loosening omelet; slide onto warm plate.
Frost with remaining sour cream.
Cut into wedges with two forks.