Step 1

Place cake on a serving plate. Cut a 1-inch horizontal layer off top of cake. Without cutting through bottom of cake, make a vertical cut 1/2 inch from outside edge of cake all the way around cake. Make another vertical cut (parallel to first cut) 1/2 inch from inside edge of cake all around cake. Gently remove cake between 2 cuts, forming a trench, and reserve removed cake for another use. Be careful not to tear bottom of cake.

Step 2

Spoon lemon curd into hollowed out cake and replace top layer.

Step 3

In a medium bowl, mix whipped topping and reserved lemon curd until smooth. Frost cake and refrigerate until ready to serve.