- 8 (1- to 1 1/4-pound) acorn squash
- 3 tablespoons vegetable oil
- 1 tablespoon kosher salt
- 1 large red onion, chopped
- 1 1/2 tablespoons vegetable oil
- 5 medium beets (2 pounds without greens), peeled and cut into 1-inch pieces
- 1 red apple such as Gala or Braeburn, peeled and cut into 1-inch pieces
- 2 garlic cloves, minced
- 4 cups chicken or vegetable broth
- 4 to 5 cups water
- 2 tablespoons cider vinegar
- 1 tablespoon packed light brown sugar
- Accompaniment: cornmeal-cayenne grissini
- Preheat oven to 375°F.
- Cut off “tops” of squash (about 1 inch from stem end) and reserve. Scoop out seeds and discard. Cut a very thin slice off bottoms of squash to create a stable base. Brush “bowls” and tops all over with oil and sprinkle salt inside. Arrange squash bowls, with tops alongside, stem ends up, in 2 large shallow baking pans.
- Roast squash in upper and lower thirds of oven, switching position of pans halfway through baking, until flesh of squash is just tender, about 1 1/4hours total.
- Cook onion in oil in a 5-quart heavy saucepan over moderate heat, stirring occasionally, until softened. Add beets and apple and cook, stirring occasionally, 5 minutes. Add garlic and cook, stirring, 30 seconds.
- Add broth and 4 cups water, then simmer, uncovered, until beets are tender, about 40 minutes. Stir in vinegar and brown sugar.
- Purée soup in 3 batches in a blender until very smooth, at least 1 minute per batch (use caution when blending hot liquids), transferring to a large bowl. Return soup to pan, then season with salt and pepper and reheat. If soup is too thick, add enough water to thin to desired consistency.
- Serve soup in squash bowls.