In a medium bowl, use an electric mixer to beat the egg yolks until thick and lemon colored; beat in ½ cup of the sour cream and the salt. Use a rubber spatula to gently fold the beaten egg whites into the mixture.
Heat the butter in 10-inch, oven-safe skillet; pour in the omelette mixture, leveling gently. Sprinkle the ham on top. Cook over low heat until lightly browned on the bottom (about 5 minutes).
Finish cooking in a preheated oven until top is golden brown (about 12 minutes).
Divide the omelette in half and slide onto two plates, garnishing with the remaining sour cream.
Notes
If you are preparing this recipe as GLUTEN-FREE, just be sure to use a brand of ham that is known to be GF.