Begin by making the cake batter according to the box's directions (including preheating the oven to the suggested temperature).

Zest one lime and leave the zest peelings on a plate - set aside.

Once batter has formed, add juice of one lime (we recommend using the juice from the lime you just grated). Mix thoroughly.

Line a muffin tin with paper liners and fill each 2/3 of the way with cupcake batter. Any leftover batter can be poured into an airtight container, refrigerated and used the next day.

Bake according to box's directions and allow to cool completely, about one hour.

In a large mixing bowl, add softened butter, confectioners' sugar and milk.

Beat on low then slowly increase to high until a buttercream forms. Fold in lime juice from half a lime.

Pipe each cupcake with lime buttercream and sprinkle with lime zest. You may also add a slice of lime on top.