Preparation Preheat broiler. Stir together onion and mayonnaise. Arrange bread slices in 1 layer on a baking sheet and broil 6 inches from heat until lightly toasted (watch carefully). Remove from oven and turn toasts over. Spread evenly with onion mixture and sprinkle with cheese and freshly ground pepper. Broil hors d’oeuvres until topping is bubbling and lightly browned, 1 to 2 minutes (watch carefully to prevent burning). Serve warm.
Preparation Preheat broiler. Stir together onion and mayonnaise. Arrange bread slices in 1 layer on a baking sheet and broil 6 inches from heat until lightly toasted (watch carefully). Remove from oven and turn toasts over. Spread evenly with onion mixture and sprinkle with cheese and freshly ground pepper. Broil hors d’oeuvres until topping is bubbling and lightly browned, 1 to 2 minutes (watch carefully to prevent burning). Serve warm.