1. Preheat the oven to 200°C. Arrange the tomatoes, onion, celery, garlic and thyme in an ovenproof dish into which they fit snugly. Drizzle with the olive oil, season generously with salt and freshly ground black pepper and bake for 40 minutes. Remove the vegetables from the oven and purée them with a stick blender. I like to scoop out a few of the cherry tomatoes and keep them whole to garnish the dish.
2. Boil the spaghetti in salted water until al dente. Drain and mix immediately with the hot tomato sauce, fish and mussels. If the yellowtail still has a hint of the butter, dill and apricot jam sauce, all the better! Garnish with fresh basil and the reserved tomatoes.