I like to use crookneck squash for this soup because it gives it a bright yellow color. Fresh ginger adds a hint of spice.
In large saucepan, heat oil over medium-high heat. Add onion and cook, stirring often, until softened, 4 to 5 minutes. Add squash, garlic and ginger. Cover and cook, stirring occasionally, until squash is tender, 10 to 20 minutes. Add broth and bring soup to a simmer.
Remove from heat and let soup cool slightly. In food processor or blender, process mixture, in batches if necessary, until smooth. Strain through fine-mesh sieve back into saucepan, using a rubber spatula to press mixture through mesh. Stir in salt.
Serve warm or chilled, thinning soup with extra broth if necessary. Ladle soup into bowls and garnish each serving with red onion and parsley.