01 - Preheat your oven to 350°F (175°C) and thoroughly grease a 9x13-inch baking pan.
02 - In a large mixing bowl, combine the white cake mix, water, vegetable oil, and eggs. Beat the mixture with an electric mixer on medium speed for two minutes until well combined.
03 - Pour the prepared batter into the greased 9x13-inch baking pan. Bake for 28 to 32 minutes, or until a toothpick inserted into the center of the cake comes out clean.
04 - Allow the cake to cool in the pan for 15 minutes before proceeding.
05 - Using the handle of a wooden spoon, carefully poke holes evenly across the entire surface of the cake, spacing them approximately 1 inch apart.
06 - In a medium bowl, fully dissolve the lime-flavored gelatin powder in 1 cup of boiling water. Once dissolved, stir in 1/2 cup of cold water.
07 - Slowly and evenly pour the prepared gelatin mixture over the warm cake, ensuring it soaks into all the poked holes.
08 - Refrigerate the cake for a minimum of 2 hours, or until it is completely chilled and the gelatin has fully set.
09 - In a small bowl, gently fold the 1 tablespoon of lime zest and the optional 2 tablespoons of powdered sugar into the thawed whipped topping.
10 - Evenly spread the flavored whipped topping over the chilled cake. Garnish with additional lime zest as desired.
11 - Slice and serve the cake chilled for best enjoyment.