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.
03 - In a large bowl, beat butter and sugar until light and fluffy, about 2–3 minutes.
04 - Add eggs one at a time, beating well after each addition. Mix in lemon zest, lemon juice, Limoncello, and vanilla extract.
05 - Add the dry ingredients in three parts, alternating with the milk, beginning and ending with the dry ingredients. Mix until just combined; do not overmix.
06 - Divide batter evenly among cupcake liners, filling each about 2/3 full.
07 - Bake 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, then transfer to a wire rack to cool completely.
08 - In a large bowl, beat the butter until creamy. Gradually add powdered sugar, beating until smooth. Add Limoncello, lemon juice, lemon zest, and salt, and beat until light and fluffy (2–3 minutes).
09 - Once cupcakes are completely cool, frost with the Limoncello frosting. Decorate with extra lemon zest if desired.