Preheat the oven to 350°F (175°C) and line a 12-cup muffin tin with paper cupcake liners.
In a large bowl whisk together the flour, baking powder, baking soda, and salt, then set aside.
In another large bowl beat the softened butter and granulated sugar with an electric mixer until light and fluffy, about 2 to 3 minutes.
Add the eggs to the butter mixture one at a time, beating well after each addition, then mix in the vanilla extract and lemon zest.
In a small bowl stir together the lemon juice, milk, and pink lemonade concentrate.
Add the dry ingredients to the butter mixture in two additions, alternating with the lemon-milk mixture, beginning and ending with the dry ingredients, mixing on low just until combined.
If using, gently mix in the pink gel food coloring one drop at a time until your desired shade is reached, taking care not to overmix the batter.
Divide the batter evenly among the 12 liners, filling each about two-thirds full.
Bake the cupcakes for 16 to 18 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
Transfer the pan to a wire rack and let the cupcakes cool in the pan for 5 minutes.
Carefully remove the cupcakes from the pan and place them directly on the wire rack to cool completely, about 25 minutes.
While the cupcakes cool, prepare the frosting by beating the softened butter in a medium bowl until smooth and creamy, about 1 minute.
Gradually add the powdered sugar, 1/2 cup at a time, beating on low to incorporate and then on medium until fluffy.
Add the pink lemonade concentrate, lemon juice, salt, and a tablespoon of cream or milk, then beat until smooth and spreadable, adding more cream or milk as needed for consistency.
If desired, tint the frosting with pink gel food coloring, beating until the color is evenly distributed.
Once the cupcakes are completely cool, transfer the frosting to a piping bag or use an offset spatula to frost each cupcake generously.
Garnish the frosted cupcakes with pink sanding sugar, sprinkles, or small lemon slices or zest curls if desired.