Beet and Apple Soup

1 large red onion, chopped ( I used 1/4)
1 1/2 tablespoons vegetable oil
5 medium beets (2 lb without greens), peeled and cut into 1-inch pieces
1 red apple such as Gala or Braeburn, peeled and cut into 1-inch pieces (used 2 small green)
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(used 2 tbs of white)

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.