Lightly oil a small 9 x 4-inch loaf pan and set it aside.
Combine the granulated sugar (1 1/2 cups plus 2 tbsp), lemon juice, and 160 ml of the water in a small saucepan and bring to a boil over medium heat.
Reduce heat and simmer without stirring for about 15 minutes, or until the mixture reaches 115°C (239°F) on a candy thermometer; then remove from heat and set aside.
In a separate small pan, whisk together the remaining water (about 2 cups total minus 160 ml used) and 5 tablespoons cornstarch until smooth, then cook over medium heat, stirring, until thickened into a gelatinous paste; remove from heat.
Gradually whisk the hot cornstarch paste into the warm sugar syrup in a thin stream, whisking constantly to combine.
Return the pan to low heat and cook gently, stirring occasionally to prevent sticking, for 40–45 minutes until the mixture becomes slightly yellowish and very thick.
Remove from heat, stir in the rose water and any desired color, mix well, then pour into the prepared loaf pan and smooth the top.
Let the pan sit overnight at room temperature to fully set.
Grease a knife, turn the set slab out if desired, and cut into small cubes. Toss the cubes in a mixture of the confectioners' sugar and the remaining 2 tablespoons cornstarch to coat and prevent sticking.
Serve the coated Turkish delight pieces.