Presoak a clay pot, top and bottom, in water for 15 minutes.
Place the salmon in the presoaked pot and add the parsley, tarragon, tomato, onion, oil, lemon, white wine, salt, and pepper.
Cover the pot and place it in cold oven.
Set the oven temperature at 480 degrees.
Cook 10 minutes for each inch of thickness of salmon, plus 15 minutes for the pot. Test the salmon for doneness by lifting the section away from bones-it should separate freely. Don't overcook! When done, pour off the liquid into a saucepan, heat to boiling and add the sour cream, capers, and arrowroot. Stir tmtil thickened and serve over the salmon.