Melt the butter in a small skillet over medium heat. Add the onion and sugar; cook 14 minutes or until golden brown, stirring frequently. Remove from heat; stir in basil.
Cut bread in half horizontally. Place bread, cut sides up, on a baking sheet. Broil the bread for 2 minutes or until toasted. Spread 1 tablespoon caramelized onion mixture over each bread half. Sprinkle each bread half with 1 tablespoon Parmesan cheese and 1/8 teaspoon black pepper. Broil for 1 minute or until cheese melts.