Melt butter in a saucepan. Add onion, garlic and sugar.
Cook over medium heat 1-2 minutes or until the onion is softened. Add broth, water, salt and pepper. Bring to a boil- stirring occasionally.
Reduce heat to low. Cook for 15 minutes, stirring occasionally. Stir in puréed pumpkin, evaporated milk and cinnamon. Cook 5 more minutes. Stirring occasionally.