For omelet, beat egg whites until stiff, but not dry; set aside.
In a large mixing bowl, beat egg yolks until thick and lemon colored. Beat in cream and salt. Fold in beaten egg whites.
Melt butter in heavy frying pan, about 9 inches in diameter, turn in eggs. Turn heat to low, and cook very slowly until eggs are golden brown on bottom, about 10 minutes.
Place in moderate oven, 350 degrees and bake about 10 minutes or until knife inserted in center comes out clean.
Loosen omelet from pan. Cut across center. Fold omelet and turn out onto serving platter.
Sprinkle top with sugar mixed with lemon peel. Slip under broiler for a few seconds until sugar melts and browns slightly. Pour some of the blueberry sauce over omelet.
Serve immediately. Pass remaining sauce.
For Hot Blueberry Sauce: Combine in a saucepan the blueberries, water, lemon juice, salt, and dash of cinnamon. Stir together sugar and cornstarch; add to blueberry mixture. Cook over moderate heat, stirring, until sauce is thickened and smooth.