Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper. In a large mixing bowl, whisk together self-rising flour, sugar, lemon zest, and ground nutmeg. Cut cold, cubed unsalted butter into the dry mixture using a pastry cutter or your fingers until it resembles coarse crumbs. Gradually mix in low-fat buttermilk until a soft dough forms. Divide the dough into two disks, flatten them slightly, and place them on the prepared baking sheet. Bake for 15 minutes, or until golden brown.

While the shortcake is baking, take your fresh raspberries and place them in a mixing bowl. Sprinkle sugar over the raspberries and add fresh lemon juice. Gently toss the mixture to ensure all the berries are coated. Let them sit for about 10-15 minutes, allowing the sugar to draw out the juices and enhance the natural sweetness of the raspberries.

Once your shortcake has cooled, pour in the heavy whipping cream in a chilled mixing bowl. Using an electric mixer, beat the cream on medium speed until soft peaks begin to form. Gradually add powdered sugar to sweeten the cream further and continue beating until stiff peaks form.

Start by chopping the baked shortcake into bite-sized pieces. In individual serving jars or cups, place a layer of shortcake pieces at the bottom. Follow this with a layer of macerated raspberries, allowing their juices to soak into the cake. Next, add a generous dollop of whipped cream on top. Repeat the layers in the same order, finishing with whipped cream.

Use any remaining raspberries to garnish the top of each trifle. Chill the assembled trifles in the refrigerator for at least 30 minutes before serving to allow the flavors to meld together.