Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the yellow cake mix, eggs, sour cream, and vegetable oil. Blend until smooth and creamy.
In a separate small bowl, mix together the packed light brown sugar and cinnamon.
Pour half of the cake batter into the prepared 9x13-inch baking pan. Evenly sprinkle the cinnamon-sugar mixture over the batter. Pour the remaining cake batter on top.
Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
Once the cake is baked, remove it from the oven and allow it to cool for about 10 minutes. Poke holes all over the surface of the cake.
In a medium bowl, whisk together the confectioners’ sugar and milk until smooth.
Pour the glaze evenly over the warm cake, allowing it to seep into the holes.
Once the glaze has settled, spread the thawed whipped topping over the entire surface of the cake.
Cover the cake and refrigerate for at least 2 hours, or overnight for the best flavor.
