1. Blanch the tomatoes (place them in boiling water for 50 seconds) then transfer them to a bowl of cold water to peel them. Cut the flesh into cubes and remove the cores.
2. Whisk together the lemon juice, vinegar, and olive oil in a bowl.
3. Mix the tomato cubes, shallots, chives, and half of the tarragon in a bowl.
4. Sauté the salmon in a pan with a little olive oil and the remaining tarragon.
5. Once the salmon is cooked, mix the contents of the 2 bowls together.
6. Serve the salmon hot and drizzle with room temperature sauce.