Begin heating the apple cider vinegar in a large saucepan over medium/low heat. While the vinegar is reducing, mix together cream, white sugar, brown sugar and salt. After five minutes the vinegar should be a darker color and cooked down to about one tablespoon. Increase the heat to medium and add the cream and sugar mixture to pan. Stir continuously until the liquid begins to boil. Stop stirring and attach your candy thermometer.While the caramel is boiling, line an 8×8 pan with buttered foil. Stir together the vanilla and cinnamon and set aside. Dip a heat resistant brush into water and wipe down the sides of the pan to remove any sugar crystals. Once the caramel reaches 237 degrees F remove from heat. (For firm caramels, heat to 245 degrees F) Quickly and carefully stir in the vanilla and cinnamon mixture. Pour into the buttered pan and cool in the refrigerator overnight.