Roasted Tomato and Zucchini Soup

The roasted flavour in this soup gives it a more robust flavour.
2 kg Roma tomatoes
olive oil
salt and pepper
1 teaspoon sugar
5 or 6 zucchini, roughly sliced
2 stalks celery, roughly chopped
1 onion, chopped
½ cup herbs (we used basil and origanum)
2 tablespoons vegetable stock powder

Cut the tomatoes in half and spread on a baking tray, cut side up. Sprinkle with olive oil and season with salt, pepper and sugar. Bake in an oven at 150°C for 1 hour. Place all the other ingredients in a pot with 2 cups of water and simmer for ½ hour. Blend and set aside. Using a potato press or a sieve, squeeze the juice out of the tomatoes and pour it into the pot with the blended ingredients. Stir, taste to check the seasoning, and serve hot with herb bread.