Grease a 13x9x2-inch baking pan with butter or nonstick spray, then set aside.
Make the cake: In a medium bowl, whisk together the flour, salt, and baking powder. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment, beat the butter and sugar until light and fluffy.
Add in the eggs, pink lemonade concentrate, lemon juice, and vanilla extract until well combined.
Mix in about half of the flour mixture and half of the milk until combined, then add the remaining flour and milk until the batter is smooth. If desired, add 2 drops of pink or red food coloring to the batter.
Spread the batter evenly into the prepared baking pan.
Bake in the preheated oven for 30-35 minutes, until a toothpick inserted into the center of the cake comes out clean. Cool completely.
While the cake cools, make the frosting. Add the butter, cream cheese, salt, pink lemonade concentrate, lemon juice, and powdered sugar to the bowl of a stand mixer fitted with the paddle attachment and beat until smooth.
Add in the pink or red food coloring, if desired, and beat until the color is incorporated.
Spread the frosting evenly over the cooled cake, decorate as desired.