Line a large baking sheet with foil or parchment paper and coat with vegetable oil spray. In a heavy, medium saucepan, mix together sugar, heavy cream, cinnamon and salt. Cook over medium heat, stirring frequently until mixture is smooth and comes to a boil. Continue cooking, stirring, until mixture reaches 236° to 240° on a candy thermometer. (A small spoonful of the mixture dropped into ice water will form a soft ball when rubbed between your index finger and thumb.)
QUICKLY stir in walnuts and vanilla extract; cook, stirring, until nuts are coated completely, 2 to 3 minutes. Working carefully, spread walnuts in a single layer on the prepared baking sheet, separating nuts with a fork. Let cool completely.