1Grease 8-inch square pan with butter. In 2-quart heavy saucepan, stir together sugar, corn syrup, sour cream, 2 tablespoons butter and the salt. Cook over medium heat, stirring constantly, until sugar is dissolved. Cook, stirring occasionally, to 234°F on candy thermometer or until small amount of mixture dropped into cup of very cold water forms a soft ball that flattens when removed from water; remove from heat. Cool without stirring to 120°F, about 1 hour. (Bottom of saucepan will be lukewarm.)
2Add vanilla, pecans and cherries. Beat vigorously and continuously with wooden spoon 5 to 10 minutes or until mixture is thick and no longer glossy. (Mixture will hold its shape when dropped from a spoon.) Quickly spread in pan. Let stand about 1 hour or until firm. Cut into 1-inch squares. Store in airtight container at room temperature.