Once cupcakes have cooled and curd is finished, use a cupcake corer to remove the centers of the cupcakes and spoon in some curd to the center of each cupcake.
Combine frosting ingredients in a large bowl or stand mixer fitted with whisk attachment and beat until light and fluffy.
Pipe frosting onto curd filled cupcakes and top with extra zest and a lime slice.
Notes
If you can't find Key Lime Yogurt, plain or vanilla can be used as a substitute, as well as sour cream.