Ingredients
Preparation
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.