Preheat oven to 350 degrees. Line a 9" x 13" cake pan with parchment paper and coat lightly with cooking spray. Set aside.
In a large bowl, sift flour, baking powder and baking soda together and set aside.
In a separate large bowl, or the bowl of a stand mixer fitted with paddle attachment, cream butter with granulated sugar together about 3–4 minutes until light and fluffy. Add eggs one at a time and beat for 30–40 seconds after each egg is added. Add vanilla extract and beat well. Gently fold the flour mixture into the butter mixture ½ cup at a time until well blended then spread batter evenly into prepared pan.
Bake 28–30 minutes then remove from oven and cool slightly on a rack. Once cake has cooled a bit but is still slightly warm, pierce cake several times with a fork or wooden skewer. In a small bowl, stir the eggnog, milk and sweetened condensed milk together then pour the milk mixture evenly over the top of the cake.
Cover with plastic wrap and refrigerate for at least 3 hours or preferably overnight. Frost top of cake with whipped cream or whipped topping and sprinkle with cinnamon. Slice and serve but be sure and keep any leftover cake covered and refrigerated. Enjoy!
I love this dessert for the holidays! It’s so incredibly festive.