Make the vinaigrette by whisking together the olive oil, lemon juice, salt & pepper chopped herbs and onion.
Put the fish in a large skillet with the stock.
Bring the liquid to a boil, then turn it off.
Let the fish rest for 20 minutes; it will be cooked.
Drain the liquid and save for another use, pat the fish dry.
Seasonwith salt and pepper, then flake it into a bowl.
Tosswith the tomatoes, greens and vinaigrette.