Step 1

Preheat oven to 350° F. Grease and flour a 9x13-inch or 11x17-inch pan.

Step 2

Blend cake mix, oil, eggs, yogurt, zest, and juice in a large bowl on low speed with an electric mixer for 30 seconds until moistened. Then beat on medium speed until smooth, 1-2 minutes.

Step 3

Pour the batter into the prepared pan and bake immediately for 27-32 minutes (for 9x13 pan) or 20-22 minutes (for 11x17 pan) or until a toothpick inserted in the middle comes out clean.

Step 4

Set the cake on a wire rack and allow it to cool 5-10 minutes.

Step 5

Add key lime juice and sugar to a small saucepan and heat over low heat gently stirring until the sugar dissolves.

Step 6

Once the cake is out of the oven and cooled a few minutes, brush syrup over the warm cake. Allow the cake to cool completely before topping.

Step 7

Once the cake is cooled completely, spread whipped topping over the top of the cooled cake. Garnish by sprinkling with key lime zest and lime slices if desired. Slice the cake and serve.