In a heavy saucepan, combine the Granulated Sugar, Water and the Cream of Tartar. Bring to a boil over medium heat, stirring until the sugar dissolves; then let the syrup simmer until it reaches the soft‑ball stage (or thickens noticeably).
Meanwhile, whisk a generous amount of Cornstarch with some additional Water until completely smooth to make a slurry; pour this into a separate large saucepan and heat gently, whisking, until it starts to thicken into a glossy paste.
Slowly pour the hot sugar syrup into the thickened cornstarch mixture in a thin stream while whisking constantly so the two combine without lumps. Add the Lemon Juice to the combined mixture to help prevent crystallization.
Lower the heat and simmer the mixture, stirring frequently, until it becomes very thick, elastic and translucent—this can take 20–40 minutes depending on quantity and heat. Be patient and keep stirring so it doesn’t stick or burn.
Remove the pan from the heat and stir in the Rose Water and a few drops of Red Food Coloring until the flavor and color are evenly distributed; adjust to taste.
Prepare a loaf pan or baking dish by generously coating the bottom and sides with a mixture of Powdered Sugar and more Cornstarch. Pour the hot Lokum mixture into the prepared pan, smooth the top, and let it cool to room temperature before covering and refrigerating or leaving at cool room temperature to fully set—ideally several hours or overnight.
When set, turn the slab out onto a surface dusted with the powdered sugar–cornstarch mix. Using a knife dusted in the same mixture, cut into small squares and toss each piece in more of the coating so they don’t stick together.
Store the Turkish Delight in an airtight container layered with the powdered sugar–cornstarch mixture to keep pieces separate; it will keep for several days at room temperature.
