Toast bread if desired. Arrange pieces on a flat microwavable plate or tray. Spread with mayonnaise. Place 1 tomato slice on each bread half. Top with tuna, onion and some alfalfa sprouts, dividing evenly. Sprinkle cheese over bread. Cover with waxed paper. Microwave cook on High power for 2 to 4 minutes, or until sandwiches are heated through and cheese is melted, rotating dish once during cooking. Serve topped with avocado slices. Garnish as desired.

Prep Time: 15 minutes