Preheat your oven to 350°F and line a muffin tin with cupcake liners.

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.

In a large mixing bowl, cream the softened butter and granulated sugar until light and fluffy.

Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract and lemon zest.

Alternate adding the dry ingredients and the milk to the butter mixture, beginning and ending with the dry ingredients. Mix until just combined.

Gently fold in the freshly squeezed lemon juice until incorporated.

Divide the batter evenly among the prepared cupcake liners, filling each about two-thirds full.

Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center of a cupcake comes out clean.

Remove the cupcakes from the oven and let them cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.

In a large mixing bowl, beat the softened butter until creamy.

Gradually add the confectioners' sugar, one cup at a time, beating well after each addition. Add the lemon juice, lemon zest, vanilla extract, and a pinch of salt. Continue beating until the frosting is light and fluffy.

Use a piping bag or spatula to apply the lemon buttercream on each cooled cupcake. Decorate with optional garnishes if desired.

Store the cupcakes in an airtight container at room temperature for up to 3 days. For longer freshness, refrigerate them, but allow them to come to room temperature before serving.