Preheat the oven to 350℉. Prepare a 9x13 cake pan and spray with nonstick cooking spray.
In a large mixing bowl, make the lemon cake according to the package directions, including the necessary ingredients listed on the box, and pour the cake batter into the prepared cake pan. Bake as directed. Let the cake cool slightly, about 15-20 minutes.
1 box (15.25 oz) lemon cake mix, ingredients called for on cake mix
Use the end of a wooden spoon to poke holes across the surface of the cake, about 1-inch apart.
In a mixing bowl, whisk together the instant lemon pudding mix and the half and half milk. Whisk until thickened and let it sit for a few minutes to thicken even more.
2 boxes (3.4 oz each) instant lemon pudding mix, 2 cups half and half
Pour or pipe the prepared lemon pudding over top the cake, ensuring to fill each hole, and spread the remaining pudding evenly over top of the cake with a spatula. Cover the pan with a lid or plastic wrap and refrigerate for at least 1 hour.
In a large bowl using an electric hand mixer, or use a stand mixer with the whisk attachment, beat the heavy whipping cream, powdered sugar, and vanilla extract until stiff peaks form. Spread the whipped topping over top the chilled cake.
2 cups heavy whipping cream, 1/2 cup powdered sugar, 1 teaspoon vanilla extract
The cake can be served right away, or chill the cake for up to 24 hours before serving. Add lemon slices and lemon zest on top of the cake (optional) right before serving.
lemon slices & fresh lemon zest