Peel core and quarter pears. Cover with water containing vinegar and salt; drain. Do not rinse. Place in boiler, cover with fresh water and cook until fork goes in fairly easily. Drain. Arrange pears in a buttered flat baking dish.
Sprinkle over pears a mixture of sugar, flour and cinnamon. Combine water, lemon juice and vanilla and pour over pears. Dot with butter. Cook 45 minutes in 400 degree oven until syrup thickens. Brown in broiler at last minute. Serves 8.