Preheat your oven to 350°F (175°C). Line the cupcake tin with cupcake liners.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In a large mixing bowl, cream the softened butter and granulated sugar until light and fluffy using an electric mixer or whisk.
Add the eggs one at a time, mixing well after each addition. Then mix in the vanilla extract and lemon zest.
In a separate bowl, combine the buttermilk and lemon juice. Gradually add the flour mixture to the butter mixture, alternating with the buttermilk mixture. Begin and end with the flour mixture. Mix until just combined.
Divide the batter evenly among the cupcake liners, filling each about two-thirds full.
Bake in the preheated oven for 16-18 minutes, or until a toothpick inserted into the center comes out clean. Let the cupcakes cool in the pan for 5 minutes, then transfer them to a cooling rack to cool completely.
While the cupcakes are cooling, make the raspberry frosting. In a mixing bowl, beat the softened butter until creamy. Gradually add the powdered sugar, followed by the vanilla extract, raspberry puree, and salt, mixing until well combined and smooth.
Once the cupcakes are completely cooled, frost them using a piping bag or a knife. Decorate with fresh raspberries or lemon zest, if desired.