8 acorn squashes (about 1 and 1/4 pounds each)
3 Tablespoons vegetable oil
1 Tablespoon kosher salt
1 large red onion, chopped
1 and 1/2 Tablespoons olive oil
5 medium beets (about 2 pounds without greens) peeled and cut into 1 inch pieces
1 red apple (such as Gala), peeled, cored and cut into 1 inch pieces
2 garlic cloves, minced
6 cups vegetable broth
1 teaspoon maple sugar
To roast the squash, preheat the oven to 375. Cut off the tops of the squash (about 1 inch from the stem end) and reserve. Scoop out the seeds and discard. Cut a thin slice off the squash bottoms to create a stable base, but do not make an opening in the bottom of the squash. Brush the vegetable oil inside and on top of the squash and sprinkle the kosher salt on the inside. Arrange the squash bowls, with tops alongside, stem ends up, in two large, shallow baking pans. Roast the squash in the upper and lower thirds of the oven, switching the positions of the pans halfway through baking, until the flesh of the squash is just tender, about 1 and 1/4 hours.
While the squash is roasting, make the soup. In a 5-quart, heavy saucepan over medium heat, cook the onion in the olive oil, stirring occasionally, 5 minutes or until the onion is softened. Add the beets and apple and cook, stirring occasionally, 5 minutes. Add the garlic and cook, stirring, 30 seconds, or until well combined. Add the broth and 2 cups water, then simmer, uncovered, until the beets are tender, about 40 minutes. Stir in the maple sugar. Puree the soup in 3 batches in a blender until very smooth, at least 1 minute per batch, transferring the soup to a large bowl. (Use caution when blending hot liquids!) Return the soup to the pan, season to taste with salt and pepper, and reheat. If the soup is too thick, add enough water to thin to the desired consistency. Serve the soup in the squash bowls.