Heat broiler to low. Combine eggs, egg whites, salt, and pepper in a bowl. Heat oil in a 12" cast iron skillet over medium-high heat. Cook onion, bell pepper and thyme, stirring occasionally, until vegetables are somewhat soft, about 3 minutes. Add asparagus and mushrooms- cook for approx. 3 minutes. Add salmon and cook until opaque, 3 minutes. Pour egg mixture into skillet; reduce heat to low. Cook, stirring occasionally, until egg begins to set but is still wet on top,approx.  7 minutes. Cover to skillet( without stirring) and allow to cook for 5 minutes. Uncover and sprinkle on cheese- transfer skillet to broiler; broil until golden, Approx. 3 minutes. Remove from broiler and slice into 4-6 wedges; serve.