This recipe is used for Golden Popcorn Squares, Congo Bars, and Pecan Caramel Shortbread and can easily be halved or doubled.
Combine sugar, cream of tartar, salt, and 2/3 cup water in a wide, heavy-bottomed saucepan, with sides at least 3 inches high. Place over high heat. Let cook, without stirring, until some sugar begins to melt and turn golden, 2 to 5 minutes. Turn heat to medium; continue to cook, stirring occasionally, until all sugar is melted, deep golden, and a candy thermometer reads 300 degrees (hard-crack stage). While stirring, pour the cream slowly down the side of the pan. When cream is incorporated, remove from heat; transfer to a heatproof bowl.