Put the sugar and lemon juice in a pan with 3/4 cup of water. Stir until the sugar dissolves. Bring to a boil. Simmer without stirring for 30 to 40 minutes, or until a small dab is soft and pliable between your fingers when it's dropped into cold water (soft ball stage or 240 on a candy thermometer).
Combine the cornstarch and cream of tartar in a large heavy-bottomed saucepan and whisk in
1 and 1/2 cups water until smooth. Cook on medium heat, stirring constantly until thick. Slowly stir in the sugar syrup. Simmer over very low heat until very thick and pale golden, 60 to 70 minutes. Stir often to ensure that your mixture isn't sticking to the pan. Brush and 8 and 1/4 by 4 and 1/2 inch dish with straight sides with oil and line with plastic wrap. Stir in the rose water and pistachios into the mixture and add the coloring drop by drop until you have a soft rose petal pink. Pour spread?!? into the dish and cool overnight, covered. Combine the confectioners sugar and cornstarch on a plate. Cut the loukoumi into 1 and 1/4 inch squares and toss in the sugar mix. It will keep for week in a covered tin or box, not an airtight container.