Preheat your oven to 350°F (175°C) and line a cupcake pan with liners.
In a bowl, whisk together flour, baking powder, baking soda, and salt.
In a separate bowl, beat butter and sugar until light and fluffy. Add eggs one at a time, mixing well.
Add lemon juice, zest, and milk, then mix until combined.
Gradually add dry ingredients to the wet mixture and mix until just combined.
Fill cupcake liners about 2/3 full and bake for 18-20 minutes, or until a toothpick comes out clean.
For the buttercream, beat butter until creamy, then add powdered sugar, lemon juice, and zest. Add milk as needed for desired consistency.
Frost cooled cupcakes and enjoy!