Whip the cream until it starts to form soft peaks. Add the powdered sugar, and then the lemon extract and lemon juice once the sugar is incorporated.
In a pint-sized mason jar, layer the berries, cream, and poundcake (if desired). The amounts are totally your preference! I like to do more berries than cream, but it's a dessert that's customizable. If you have guests, you can even have all the ingredients out like a buffet, and they can create their own trifle.