Combine sugar, orange rind, juice, and cinnamon in a small saucepan; bring to a boil. Reduce heat, and simmer 8 minutes or until syrupy.
Spread one side of each bread slice with butter; place bread, buttered side up, on baking sheet. Spread 1 tablespoon sugar mixture over each slice.
Broil 4 inches from heating element until browned. Serve immediately.