Almost-Instant Chilled Borscht

In a medium saucepan, heat the canola oil. Add the onion and cook over moderate heat until softened, 3 minutes. Add the beets and cook, stirring, until crisp-tender, 3 minutes. Add the carrots, season with salt and pepper and cook until crisp-tender, 3 minutes. Add the vinegar and cook until evaporated. Add the beet juice and immediately transfer to a bowl. Set the bowl in a bowl of ice water to chill. Serve the borscht in small bowls, garnished with horseradish, sour cream and dill.