Preheat your oven to 350°F (175°C) and line a 12-cup muffin pan with cupcake liners.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In a large bowl, use an electric mixer to cream the softened butter and sugar together until light and fluffy, about 3-4 minutes.
Add the eggs one at a time, mixing well after each addition. Then, mix in the vanilla extract and lemon zest until combined.
Gradually add the dry ingredients to the butter mixture, alternating with the buttermilk, starting and ending with the flour mixture. Beat until just combined.
Gently fold in the fresh raspberries and the lemon juice, being careful not to crush the berries.
Divide the batter evenly among the prepared cupcake liners, filling each about two-thirds full.
Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Allow cupcakes to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.
In a large bowl, beat the softened butter with an electric mixer until smooth and creamy. Gradually add the powdered sugar, lemon juice, and lemon zest. If the frosting is too thick, add a tablespoon of heavy cream until desired consistency is reached.
Once the cupcakes are completely cool, frost them generously with the lemon frosting using a piping bag or a spatula.
Top each cupcake with a fresh raspberry for decoration.
Notes
For best results, use fresh raspberries and ensure the butter is softened.