Pour 1/2 l of boiling water over the tomatoes and leave to soak for about 15 minutes. In the meantime peel and chop the onion. Peel, wash and chop carrots and potatoes. Squeeze oranges and measure 1/4 l.
Heat the oil in a large pot. Sauté the onion in it. Steam potatoes and carrots briefly. Sprinkle with 1 tbsp. sugar and caramelise briefly. Add 1/2 l water, orange juice, tomatoes and soaking water.
Bring everything to the boil, stir in broth and simmer covered for about 25 minutes.
Puree the soup with a hand blender. Season to taste with salt, pepper and sugar.
For the milk foam, wash the rosemary and dab dry. Pluck needles and chop roughly. Warm the milk and rosemary and froth it up (e.g. with a milk frother or hand blender).
Serve the soup with the milk foam.