Preheat the oven to 350°F (175°C). Grease a 9x13 inch baking pan.
In a mixing bowl, combine the yellow cake mix, pumpkin puree, vegetable oil, eggs, and pumpkin pie spice. Mix until well combined.
Pour the batter into the prepared baking pan and spread evenly.
Drizzle the sweetened condensed milk over the batter.
Bake for 30 minutes or until a toothpick inserted into the center comes out clean.
While the cake is baking, prepare the frosting. In a bowl, beat the cream cheese and butter until smooth. Gradually add the powdered sugar and vanilla extract, mixing until creamy.
Once the cake has cooled, spread the cream cheese frosting evenly over the top. Slice and serve.
Notes
Store leftover cake in the refrigerator for up to 3 days.