Wash the carrots and remove the greens. Peel onion and cut larger specimens in half. Peel woody ends of asparagus, then cut asparagus into pieces about 5 cm long.
Heat oil in a large pan and sauté carrots in it. Add water and soup and sauté for another 5 minutes. Mix in asparagus and onion and steam together for another 5 minutes. Remove vegetables.
In another large saucepan, lightly caramelize sugar, then pour in hot vegetable stock and vinegar. Stir constantly while doing this. Add salt, pepper and lemon zest to taste. Add the vegetables to the pan and mix thoroughly with the sauce. Heat again briefly so that the vegetables mix well with the marinade.
Divide the vegetables between two plates and serve.