Tomato Scallion Omelet

Turn on broiler. Melt half the butter in a heavy ovenproof skillet over medium high heat. Sauté onion about 4 minutes or until onion turns translucent. Transfer to a bowl and set aside. Melt remaining butter in skillet. Add eggs and salt and pepper to taste and cook about 1 minute until edges are just set. Tilt skillet and lift edge of omelet so uncooked eggs will flow under. Cook another 2 minutes. Sprinkle sautéed onion and remaining ingredients over omelet. Place omelet under broiler 2-3 minutes or until cheese is melted.