Preheat your oven to 350 degrees Fahrenheit. This step is crucial for ensuring that your cake bakes evenly. Make sure your oven is fully heated before placing your cake inside.
Prepare a 9x13x3-inch baking dish by spraying it with pan spray. This will help prevent the cake from sticking and ensure easy removal once it’s baked.
In a large mixing bowl, combine the 1 (14.25 oz) box vanilla cake mix, ⅓ cup vegetable oil, 1 cup eggnog, and 3 large eggs. Mix these ingredients well, using a hand mixer or a stand mixer fitted with a paddle attachment. Beat at medium-high speed for about 2 minutes, until the mixture is smooth and well combined.
Pour the cake batter into the prepared baking dish. Ensure that it is spread evenly across the dish to promote even baking.
Place the baking dish in the oven and bake for 30 to 35 minutes, or according to the directions on the box of the cake mix. Keep an eye on it; the cake is done when a toothpick inserted into the center comes out clean.
Once the cake is baked, remove it from the oven and let it cool completely in the pan. This cooling process is essential to prevent the pudding mixture from melting when poured over the cake.
After the cake has cooled, use the clean handle of a wooden spoon to poke holes all over the cake. Space the holes about one inch apart. This will allow the pudding mixture to seep into the cake, creating a moist and flavorful dessert.
In a large bowl, whisk together the 1 (3.2-ounce) box instant vanilla pudding, 3 cups eggnog, and ¼ teaspoon ground nutmeg. Let this mixture sit for about 5 minutes to thicken slightly.
Pour the pudding mixture over the top of the cake, making sure to spread it out evenly. The pudding should flow into the holes you created, infusing the cake with flavor.
Cover the cake and chill it in the refrigerator for about 2 hours. This chilling time allows the pudding to fully set and meld with the cake.
Before serving, top the cake with 1 (8-ounce) container whipped topping, spreading it out evenly across the top. Finally, dust the top with freshly grated nutmeg and a sprinkle of ground cinnamon for an inviting finish.
