Pre-heat the oven to 200°C/400°F/Gas Mark 6. On a medium heat, in a large saucepan, soften the onions and thyme in the olive oil for 3-4 minutes, without letting them colour. Add the garlic, red peppers, courgettes, aubergine, 8 pinches of salt and 4 pinches of pepper and cook for 2 minutes longer. Stir in the tomato purée and chopped tomatoes. Cook over a medium heat, with a lid on, for 15-20 minutes, until the vegetables are tender. Taste and correct the seasoning if necessary, then set aside.
Making the tomato coulis
In a blender, or with a hand-held blender, purée the cherry tomatoes with the extra-virgin olive oil, 2 pinches of salt and a pinch of pepper. Taste and add the sugar if necessary, then strain and set aside. Frying the sea bream.
Slash each fillet 3 times with a sharp knife (this allows the heat to penetrate more easily). Season with 4 pinches of salt and 2 of pepper. Over a high heat, in a large, oven-proof frying pan, heat the oil. Sear the fillets on the flesh side for 30-40 seconds in the hot olive oil. Turn the fillets over and cook for 2-3 minutes. Transfer to the oven and cook for 2-3 minutes longer, depending on thickness. Taste and correct the seasoning, if necessary, then sprinkle the lemon juice over the fillets.
Finishing the dish
Reheat the ratatouille and gently warm the tomato coulis, making sure it does not boil (if it did it would become grainy and lose all its freshness). Arrange the ratatouille in the middle of 4 soup plates and top with the sea bream fillets. Spoon the tomato coulis around and then drizzle with the best extra-virgin olive oil.