Preheat oven to 350 degrees F. Line 2 muffin tins with 24 paper liners. Set aside.

Combine the cake mix, buttermilk, lemon juice, lemon zest, oil, and eggs with an electric mixer until combined, 2 minutes. Portion the batter evenly among the muffin cups, filling about 3/4 full. Bake for 16-20 minutes or until a toothpick inserted near the center comes out clean or with moist crumbs. Cool completely.

For the frosting: Combine the butter and vanilla extract together in the bowl of a stand mixer and beat until fluffy, 2 minutes. Add in the freeze-dried raspberry powder and beat slow until incorporated. Gradually add in the confectioners' sugar, one cup at a time, alternating with the heavy cream until frosting is light and fluffy.

Pipe or spread the frosting onto the cooled cupcakes. Garnish with a fresh raspberry, if desired.