MELT butter in large saucepan over medium heat. Add onion, garlic and sugar; cook for 1 to 2 minutes or until soft. Add broth, water, salt and pepper; bring to a boil, stirring occasionally. Reduce heat to low; cook, stirring occasionally, for 15 minutes. Stir in pumpkin, evaporated milk and cinnamon. Cook, stirring occasionally, for 5 minutes. Remove from heat.
TRANSFER mixture to food processor or blender (in batches, if necessary); process until smooth. Return to saucepan. Serve warm.