01 - Preheat oven to 350°F. Line a 12-cup muffin tin with paper liners.
02 - In a medium bowl, whisk together flour, baking powder, and salt until well blended.
03 - In a large bowl, beat butter and sugar with an electric mixer until light and fluffy, approximately 3 minutes.
04 - Add eggs one at a time, beating thoroughly after each addition. Mix in lemon zest and vanilla extract until incorporated.
05 - Mix in lemon juice. The batter may appear slightly curdled—this is normal and will resolve during mixing.
06 - Add half of the flour mixture, then half of the milk, mixing on low speed. Repeat with remaining flour mixture and milk, mixing just until combined. Do not overmix.
07 - Divide batter evenly among cupcake liners, filling each about two-thirds full.
08 - Bake for 16–18 minutes, or until a toothpick inserted into the center comes out clean. Cool cupcakes in tin for 5 minutes, then transfer to a wire rack to cool completely.
09 - Once cooled, use a small knife or cupcake corer to remove a small core from the center of each cupcake. Fill the cavity with approximately 1 teaspoon of raspberry preserves.
10 - Beat butter until creamy. Add powdered sugar, lemon juice, lemon zest, and salt. Beat until smooth and fluffy, adding milk as needed to reach spreadable consistency.
11 - Pipe or spread buttercream onto filled cupcakes. Decorate with fresh raspberries or additional lemon zest if desired.