Preheat the oven to 350 degrees. Using a towel, grasp and oyster in the palm of your hand. Press the oyster, rounded-side down, on a firm surface, still holding it with the towel. Shuck the oyster by wedging the tip of an oyster knife (regular knives are too thin-bladed) between the halves of the shell, at the shell's narrowest end. When the knife tip is securely wedged, rotate the blade to pry open the shell. Slide the knife blade along the length of the shell to open completely. Remove the oyster from the shell and reserve, along with its juice. From each pair of oyster shells, save the one that is most concave on the inside, and discard the one that is flatter. Place the concave shells in a pan of cold water and scrub inside and out. Place the clean oyster shells on a cookie sheet and set aside.
Dip the tomatoes briefly in boiling water to loosen the skins, then in ice water. Peel, cut in half, remove and discard the seeds, and dice.
Have the remaining ingredients measured and ready beside the stove. When you are ready to begin cooking the oysters, place the cookie sheet containing the oyster shells in the oven. On the top of the stove, melt the butter in a hot saute pan until it begins to foam. Add the shallots, the oysters and their juice and the white wine. Cook the oysters 30 seconds, then add the heavy cream. Bring to a quick boil, then reduce to a simmer just 1 minute more, or until the oysters' edges begin to curl. Add the tomato, tarragon and bacon. Heat another 30 seconds, then remove promptly from the heat.
Remove the oyster shells from the oven and arrange 6 on each plate. Spoon 1 oyster into each shell and spoon a little of the sauce over each.
A nice variation of this recipe is to place a "nest" of steamed spinach in each oyster shell before adding the oysters and sauce. Serve with Melba Toast, brioche toast points or toast points of country bread.