This jellylike sweet is traditionally flavored with rose water. When pouring the syrup into the cornstarch mixture, be careful not to let the mixture coat the sides of the pan.
Oil an 8-inch-square baking pan, and set aside. Place the sugar, 1 cup water, and lemon juice in a small saucepan, and stir to combine. Place over medium-high heat, and bring to a boil. If there are sugar crystals on the side of the pan, brush down with a pastry brush dipped in water. Clip on a candy thermometer, and heat to 240 degrees. Remove sugar syrup from the heat, and set aside.
Combine 3/4 cup cornstarch, cream of tartar, and 3/4 cup water in a medium saucepan, and whisk until smooth and fully combined. Bring the remaining 1 1/2 cups water to a boil in a separate pan; add to cornstarch mixture, whisking constantly. Place over medium heat, and cook, whisking constantly, until the mixture becomes quite thick and just comes to a boil.
Pour the sugar syrup into the cornstarch mixture, whisking constantly, and reduce heat to medium. Gently simmer for 1 hour 15 minutes, stirring frequently.
Stir in rose water, food coloring, and almonds, if using. Pour into the prepared pan, and let set overnight. Combine the confectioners' sugar with the remaining 1/4 cup cornstarch. Sprinkle some of the mixture in an even layer over a cutting board, and unmold the Turkish delight onto it. Sprinkle the top of the candy with more of the sugar mixture. Using a sharp knife, cut into 1-inch squares. Let sit uncovered overnight. Just before serving, dust with the remaining sugar mixture. Store at room temperature in an airtight container for up to 2 weeks.