In a mixing bowl, whisk together the instant lemon pudding mix and cold milk for 2 minutes, or until smooth and thickened. Let it sit for 5 minutes to fully set.
If desired, toss the raspberries with powdered sugar to enhance their sweetness. Set aside.
In the bottom of a trifle dish or individual serving glasses, place a layer of cubed pound cake. Top with a layer of lemon pudding, followed by a layer of raspberries, and then a layer of whipped topping.
Repeat the layers (cake, pudding, raspberries, whipped topping) until all the ingredients are used, finishing with whipped topping on top.
Decorate the top of the trifle with fresh raspberries, a sprinkle of lemon zest, and a few mint leaves for a pop of color.
Cover the trifle with plastic wrap and refrigerate for at least 2 hours, or overnight, to allow the flavors to meld. Serve chilled.
