Preheat oven to 350°F. Place bread shapes on 2 large baking sheets and bake until toasted, 6 minutes.
Preheat broiler to high and place a rack 2 inches from heat source. Combine cheese, mayonnaise, pimientos, garlic and cayenne. (Mixture can be made 1 day ahead. Cover and chill.)
Spoon cheese mixture into a small baking dish and broil until mixture is bubbly and top is lightly browned, about 2 minutes.
