HEAT butter in 6- to 8-inch nonstick omelet pan or skillet over medium-high heat until hot. ADD mushrooms; SAUTE until tender, four to five minutes. ADD tomatoes; SAUTE until heated through, one minute. REMOVE from pan; KEEP warm. CLEAN pan.
BEAT eggs and dressing in small bowl until blended. HEAT omelet pan over medium-high heat until hot. POUR in egg mixture. Mixture should set immediately at edges.
Gently PUSH cooked portions from edges toward the center with inverted turner so that uncooked eggs can reach the hot pan surface. CONTINUE cooking, tilting pan and gently moving cooked portions as needed.
When top surface of eggs is thickened and no visible liquid egg remains, PLACE mushroom filling on one side of the omelet; SPRINKLE with cheese and parsley. FOLD omelet in half with turner. With a quick flip of the wrist, turn pan and INVERT or SLIDE omelet onto plate. SERVE immediately.
For a spicier omelet, use Ranch Sriracha flavored dressing.
This recipe is an excellent source of protein, vitamin A, folate and choline, and a good source of vitamin D.