Preheat your oven to 350°F (175°C). Line a muffin tin with cupcake liners.

In a large bowl, cream together the softened butter and granulated sugar until light and fluffy.

Add in the eggs one at a time, mixing well after each addition, then stir in vanilla extract and lemon zest.

In another bowl, whisk together flour, baking powder, baking soda, and salt.

Gradually add the flour mixture to the butter mixture, alternating with the buttermilk. Mix until just combined.

Prepare the raspberry swirl by blending fresh raspberries, sugar, and lemon juice until smooth.

Fill each cupcake liner about two-thirds full with the batter.

Drop spoonfuls of the raspberry mixture onto each cupcake and gently swirl with a toothpick.

Bake for 20-25 minutes or until a toothpick inserted in the center comes out clean.

Let them cool in the pan for about 5 minutes, then transfer to a wire rack to cool completely.

Beat together softened butter, powdered sugar, lemon juice, vanilla extract, and lemon zest until fluffy and creamy.

Frost the cooled cupcakes using a piping bag or spatula and garnish with a fresh raspberry.