Preheat the oven to 220 C gas 7 and lightly butter a shallow gratin dish.
Put the cream and tarragon in a saucepan and bring to the boil. Lower the heat and simmer until the cream has thickened and reduced by half, then strain and reserve.
Cover the tomatoes with boiling water for a few seconds, then peel and cut into 1 cm thick slices. Layer and generously season the tomato slices in the gratin dish.
Pour over the reduced cream, sprinkle with the cheese and place in the preheated oven. Bake for 15 minutes and serve.