It is very important that the right cornstarch be used. There are two types available in some countries — one is made from corn/maize; the other is made from wheat and called wheaten corn flour. Use the one made from corn, otherwise your Turkish delight will not remain thick during the lengthy cooking.
<p><strong>Note: </strong>Try these variations.</p>
<p>Crème de menthe: Replace the rosewater and red food coloring with 2 tablespoons crème de menthe liqueur and a little green food coloring. Omit the nuts.</p>
<p>Orange: Use 1-2 tablespoons orange flower water instead of rosewater; use orange food coloring.</p>
<p>Vanilla: Use 2 teaspoons vanilla extract instead of rosewater and coloring, and stir in ½ cup toasted chopped almonds or chopped walnuts. Do not blanch the almonds.</p>
Combine the sugar, lemon juice, and 1 ½ cups of the water in a heavy-bottomed saucepan. Stir over low heat until the sugar has dissolved, brushing the sugar crystals off the side of the pan with a bristle brush dipped in cold water.
Bring the syrup to a boil. Boil to the soft ball stage (240 degrees on a sugar thermometer), when a small spoonful of the syrup forms a ball when dropped into a bowl of very cold water. Remove from the heat.
In another heavy-bottomed saucepan, mix together the 1 cup of the cornstarch, cream of tartar, and 1 cup of the water until smooth. Boil the remaining water in another pot and stir into the cornstarch mixture.
Place over the heat and stir constantly until the mixture thickens and bubbles; use a balloon whisk if any lumps form. Gradually pour the hot syrup into the cornstarch mixture, stirring constantly.
Bring to a boil, then boil gently for 1 ¼ hours. Stir occasionally with a wooden spoon and cook until the mixture is a pale golden color. (Stirring is essential during this time.)
Stir in the rosewater to taste, and a few drops of red food coloring to tinge it a pale pink. Mix in the nuts, if using, and remove from the heat.
Lightly coat a 9-inch square cake pan with oil and pour in the mixture. Leave for 12 hours to set.
To finish the Turkish delight, combine the confectioners' sugar and remaining cornstarch in a flat dish. Lightly oil a knife and cut the Turkish delight into squares, then gently toss in the confectioners' sugar mixture.
Store in a sealed container, with the remaining confectioners' sugar mixture sprinkled between the layers.