Grease an ovenproof glass or other rectangular baking dish. Spread the diced tomato over the bottom and sprinkle with salt. Lay each okra flat over the tomato in one or more layers. Pour the water over all. Bake in a preheated 350F oven about 45 minutes, enough to cook okra but not long enough to dissolve it into mush. Do not stir during baking. Remove dish from oven and pour the lemon juice on top. Serve immediately.