Thinly slice onions and cheese. Cut bread into 3 cm slices and toast. In dutch oven, cook onions and sugar in hot oil over medium heat for 15 to 20 minutes or until deep golden brown, stirring frequently to prevent burning. Slowly add broth and pepper; bring to a boil. Reduce heat, cover, and cook slowly for 20 minutes.
Laddle into ovenproof container or individual ovenproof bowls. Place bread slices on top and add cheese. Place under broiler 3 to 10 cm from heat and cook 3 to 5 minutes until cheese is hot and bubbly.