Preheat the oven to 450 degrees F.
Cover the bottom of a medium-size sheet pan with tomato slices. Season the tomatoes with salt, and pepper, to taste and drizzle with olive oil. Place the cheese slices over the tomatoes and bake in the oven until bubbly and lightly toasted on top, about 10 minutes. Take the pan out of the oven and sprinkle with fresh oregano leaves to taste and serve with warm toasted bread.