Cut the tomatoes into 5 mm thick slices, place them on an oiled tray, sprinkle with plucked basil, season with salt and a pinch of sugar. Put the tomatoes in the oven heated to 80 °C (convection oven) and let them melt in about 1-2 hours.
Put the plucked watercress (a few leaves aside) in a blender jug, add 2/3 of the pine nuts, add grape seed oil, season with salt & pepper and a little bit of lemon juice and blend finely.
Cook the macaroni in boiling salted water until al dente.
Cut the baguette into thin slices and toast on both sides in a frying pan with olive oil. Drain on kitchen paper.
Bring the vegetable soup to the boil, add the drained macaroni, the pesto and the remaining watercress leaves and toss briefly. Add the Parmesan cheese and the remaining pine nuts and serve. Cover the slices of bread with the melted tomatoes and serve.