Preheat oven to 350ºF.

Beat egg whites until stiff peaks form. Beat egg yolks until thick and lemon-colored; stir in Canadian-style bacon, cheese, half of the basil, and pepper. Fold yolk mixture into egg whites.

In a 10-inch skillet with oven-proof handle, heat 2 teaspoons of the butter over medium heat till a drop of water sizzles. Spoon egg mixture into skillet, gently smoothing surface. Reduce heat to low; cook for 7 to 8 minutes or until the bottom is golden.

Bake in oven for 10-12 minutes or until knife inserted halfway between center and outer edge comes out clean.

Meanwhile, in skillet cook mushrooms and green pepper in the remaining hot butter over medium heat 3 minutes or until tender. Add the remaining basil and tomato; cook 5 minutes or till liquid is reduced, stirring occasionally.

Loosen sides of omelet with spatula. Make a shallow cut across omelet, cutting slightly off-center. Spoon filling over larger half. Tip skillet and fold the smaller portion of omelet over larger half. Slip omelet onto a warm serving platter. Serve immediately.