Place the oil in a large saucepan and heat over low heat.
When the oil is heated, stir in the onion, celery, and carrots and mix with a wooden spoon until soft and faintly colored, which could take up to 10 minutes.
Add 2 tsps. of tomato purée and stir until the vegetables turn to red.
Add the tomatoes, a good pinch of sugar and some ground black pepper to the pan.
Tear each bay leaf into small pieces with your hand and add to the mixture.
Stir and mix everything together, then cover for 10 minutes, still over low heat, until tomatoes shrink down and their juices flow. Give the saucepan a shake every now and then to keep things mixed.
Stir in the stock slowly while stirring at the same time to mix it with the vegetables.
Turn the heat to high and bring to a boil, then cover the saucepan, lower the heat and let it simmer for 25 minutes while stirring occasionally.
Remove saucepan from heat, uncover and let stand for a minute, then pick up the bay leaves and throw them away.
Add the soup in a blender until it is 3/4 full and blend thoroughly. Repeat with the remaining soup in the saucepan.
Pour the puréed soup in the saucepan once more and reheat.
Add salt, pepper, and sugar if needed.
If the color is not deep enough, add another tsp or so of the tomato purée and stir to dissolve.
Serve into your soup bowls.