Preheat oven to 350°F (175°C). Line a 12-cup muffin tin with cupcake liners.

In a medium bowl, whisk together flour, baking powder, and salt.

In a large bowl, cream together butter and sugar until light and fluffy. Beat in eggs one at a time, then stir in lemon zest and lemon juice.

Gradually add the dry ingredients to the wet ingredients, alternating with milk, beginning and ending with dry ingredients. Beat until just combined.

Fill cupcake liners 2/3 full. Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.

Let cupcakes cool in the tin for a few minutes before transferring them to a wire rack to cool completely.

In a large bowl, beat together powdered sugar, butter, lemon juice, and lemon zest until smooth and creamy.

Frost cooled cupcakes.