Make Dusting Powder -Line baking dish with parchment paper. Combine powdered sugar and cornstarch in a small bowl. Sprinkle about 2 tsps over the bottom and sides of the baking dish.
Make Sugar Syrup - Combine superfine sugar, lemon juice, water in a saucepan over medium-low heat. Heat gently until sugar is dissolved being careful not to reach a simmer.
Cook Base - In a small bowl, combine cornstarch with ½ cup cold water. Whisk into sugar syrup along with gelatin. Bring to a boil and then reduce heat to medium and simmer 20 minutes, stirring to eliminate any lumps. The liquid is ready when it thickens and turns a pale yellow. It should be at 250℉ when inserting an instant read thermometer.
Flavor and Set - Remove pan from heat to cool for 5 minutes. Stir in the rose water and red food coloring, if using. Pour mixture into the prepared baking dish. Leave on counter to set for anywhere from 12 hours (ideal) to 24 hours.
Form Cubes - Dust a cutting board with some of the dusting mixture and then invert the Lokum on top of it. Remove the parchment. Using a long sharp knife or bench scraper. Cut straight down from top to bottom without dragging knife. Cut cubes that appeal to you in size. Dust each cube lightly in dusting mixture to coat.
Dry Cubes - Place cubes on a parchment lined baking pan, leaving little space between each. Leave baking pan on counter for 24 hours to dry cubes. Sprinkle remaining dusting mixture over cubes and you've got Turkish Delight that's ready to eat.