**Prepare the lemon pudding**
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.
**Prepare the raspberries**
If desired, toss the raspberries with powdered sugar to enhance their sweetness. Set aside.
**Layer the trifle**
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**
Repeat the layers (cake, pudding, raspberries, whipped topping) until all the ingredients are used, finishing with whipped topping on top.
**Garnish**
Decorate the top of the trifle with fresh raspberries, a sprinkle of lemon zest, and a few mint leaves for a pop of color.
**Chill and serve**
Cover the trifle with plastic wrap and refrigerate for at least 2 hours, or overnight, to allow the flavors to meld. Serve chilled.