Preheat the oven to 350F. Grease a 9x13" baking dish and set aside.
Add the cake mix, lemonade, water, oil, eggs, lemon extract, zest of a lemon and pink food coloring to a large mixing bowl of a stand-up mixer.
Start low and increase speed beating on medium for 2 min.
Pour the batter into the prepared baking dish. Bake for 25-30 min. or as per instructions on the box or until a toothpick inserted in the middle comes out clean.
Cool in pan completely on a wire rack and make the frosting.
For the buttercream:
In a bowl of a stand-up mixer slowly whip the softened butter.
Add the icing sugar slowly until all is incorporated. Then add the lemonade, lemon extract, and food coloring and beat on medium-high until fluffy.
If still too thick then add a bit of water, 1/2 Tbsp. at a time to desired thickness.
Once the cake is cooled completely you can ice with the buttercream.