01 - Preheat oven to 350°F. Line a 12-cup muffin tin with paper liners.
02 - Whisk together flour, baking powder, and salt in a medium bowl.
03 - Beat butter and sugar with an electric mixer until light and fluffy, about 3 minutes.
04 - Add eggs one at a time, beating well after each addition. Mix in lemon zest and vanilla extract.
05 - Mix in lemon juice. The batter may look slightly curdled—this is normal.
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.
07 - Divide batter evenly among cupcake liners, filling each about 2/3 full.
08 - Bake 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 - Use a small knife or cupcake corer to remove a small core from the center of each cooled cupcake. Fill the cavity with about 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 a spreadable consistency.
11 - Pipe or spread buttercream onto filled cupcakes. Decorate with fresh raspberries or lemon zest if desired.