Using electric mixer, beat egg whites until soft peaks form. Combine egg yolks, mayonnaise and water; beat until smooth. Fold into egg whites. Place butter in a 9" glass pie plate. Microwave on high 15 seconds or until melted. Spread butter over bottom of pie plate. Carefully pour egg mixture into pie plate. Microwave on medium for 5 1/2 minutes. Sprinkle half of omelet with cheese and filling(s). Fold omelet in half using a spatula. Microwave on medium for 1 minute. 1 to 2 servings.