This super simple soup begins by roasting a red Kuri squash. Then you sauté onions until deeply fragrant before tossing in the roasted squash, and simmering it altogether with broth until done.
Heat the oven to 400 F, and line a rimmed baking sheet with parchment paper.
Split the squash in half, and then scoop out its seeds. Place the squash cut-side down on the parchment-lined baking sheet, and bake until tender - about 20 minutes.
Set the baking sheet on the counter, and allow it to rest until the squash is cool enough to handle comfortably.
Assembling the soup.
Warm the olive oil in a Dutch oven over medium heat, and then toss in the onion. Sprinkle the onion with salt, and then let it cook, stirring occasionally, until deeply fragrant - about 5 minutes.
Gently scoop the squash's flesh from its skin, and then drop it into the Dutch oven, discarding the skin. Increase the heat to medium-high, and then pour in the broth. Bring it all to a boil, and then turn the heat down to medium-low and simmer about 20 minutes or until the ingredients are cooked through and the flavors meld.
Turn off the heat, and purée the soup with an immersion blender until smooth. Ladle into soup bowls and serve hot, or transfer it to an airtight container and store it in the refrigerator up to 5 days.