Preheat oven to 425 degrees F. Line a baking sheet with foil. In a bowl combine butter, garlic, and 1/2 teaspoon of the rosemary. Lightly spread butter mixture on one side of each bread slice. Place bread slices on foil-lined baking sheet. Bake for 7 minutes or until just beginning to toast. Remove from oven.
Place a tomato slice on the buttered side of each bread slice; top each with a piece of cheese. Sprinkle with the remaining 1/2 teaspoon rosemary and ground black pepper.
Bake 3 to 4 minutes more or until cheese is starting to melt. Serve warm.