1. For the roast tomato sauce, preheat the oven to 200°C (180°C fan-forced). Put the tomatoes on a baking tray, drizzle with the extra virgin olive oil and red wine vinegar, and sprinkle on the tarragon, thyme and seasoning. Roast for 30-40 minutes, or until the skin starts to blister and peel. 

2. Remove tomatoes from oven. Use tongs to carefully peel away the tomato skin and discard. Pass the tomatoes through a food mill or a sieve, place the resulting sauce into a saucepan, and reduce for 45 minutes over very low heat. Check the seasoning; if the sauce is a little tart, add a pinch of sugar and more salt.

3. Place the fish fillets on a board. Using the back of a knife, scrape the skin to remove moisture, then wipe with kitchen paper. This helps produce a crisp skin and is an important step. 

4. Heat a heavy-based ovenproof frying pan to hot; add the 2 tablespoons of olive oil. Place the fillets skin-side down. Place a pot filled with water on top of the fish. It should be heavy enough to balance there quite nicely without breaking up the fish. This downward pressure keeps the skin in hard contact with the heat and makes it super-crisp. Sear for 5 minutes, then remove the pot and carefully turn each fillet over. (Do not use the pot for weight again.) Cook for a further 2 minutes and remove from the heat. One minute's rest should result in the fish being medium-rare, with crisp skin.

5. Heat the roast tomato sauce in a small saucepan.

6. Divide the sauce among four plates. Carefully place a fillet onto the sauce on each plate and squeeze fresh lemon juice over each piece, along with a good grind of fresh pepper. Serve immediately with a green salad.