Line a 9x13 inch baking pan with parchment paper, leaving a slight overhang.
Make cake and pour batter into the prepared 9x13 inch baking pan, preparing according to the instructions on the back of the box.
13.25 ounce boxed lemon cake mix, Ingredients needed to make cake
After baking and while cake is still warm, use a thick skewer or handle of a wooden spoon to evenly poke holes in the cake.
Allow cake to cool completely.
Remove cake from the pan and place on a large serving platter.
Pour lemon curd over top, and gently spread it into the holes.
1 ½ cups lemon curd
Cover with plastic wrap and chill in the fridge for at least 1 hour to let the lemon curd set up.
When ready to serve the cake, top with whipped topping.
8 ounce container frozen whipped topping
Garnish with fresh lemon slices.
Notes
Lemon cake mix: Feel free to use your favorite brand of lemon cake mix. Or you can make a homemade lemon sheet cake and then continue with the recipe as-written.
Lemon curd:Lemon curd is surprisingly easy to make. You can also use store bought lemon curd if you prefer.
Whipped topping: You can use Cool Whip, TruWhip, or another brand of frozen whipped topping. You could also spread the cake with homemade whipped cream if you're serving and consuming the cake right away.