Line a 15-by-10-by-1-inch baking pan with ungreased parchment paper. Prepare cake mix according to package directions. Spread batter evenly in prepared pan. Bake at 350 degrees for 24–26 minutes or until top is lightly browned.
Sprinkle sugar over a waxed paper-lined baking sheet. Immediately invert cake onto baking sheet. Gently peel off parchment paper; cool completely.
Dissolve gelatin in boiling water. Stir in jam until melted. With a fork, poke cake at 1/2 inch intervals. Brush with gelatin mixture; chill for 10 minutes.
In a bowl, beat cream cheese, milk and lemon juice. Add whipped topping and pudding mix; whisk well. Reserve 1 cup.
Place remaining pudding mixture in a pastry bag with a large star tip. Trim edges of cake.
Cut width-wise into 3 equal rectangles; place one on serving plate. Spread 1/2 cup reserved pudding mixture in center. Pipe pudding mixture around top edge of cake. Repeat with second cake layer. Top with remaining cake layer. Pipe pudding mixture along top edges. Fill center with fruit. Sprinkle with lemon peel. Store in refrigerator.